Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.93	7.405%	$137.4032	$137.40	$137.40	$137.40
Purchase #2	$226.37	8.437%	$245.4688	$245.47	$245.45	$245.50
Purchase #3	$208.48	6.501%	$222.0333	$222.03	$222.05	$222.00
Purchase #4	$197.38	12.666%	$222.3802	$222.38	$222.40	$222.40
Purchase #5	$229.54	10.683%	$254.0618	$254.06	$254.05	$254.10
Purchase #6	$143.73	12.323%	$161.4418	$161.44	$161.45	$161.40
Purchase #7	$198.91	7.444%	$213.7169	$213.72	$213.70	$213.70
7 purchase totals =	$1,332.34		$1,456.5060	$1,456.50	$1,456.50	$1,456.50