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	$56.47	4.686%	$59.1162	$59.12	$59.10	$59.10
Purchase #2	$187.42	13.732%	$213.1565	$213.16	$213.15	$213.20
Purchase #3	$178.29	9.821%	$195.7999	$195.80	$195.80	$195.80
Purchase #4	$133.26	5.399%	$140.4547	$140.45	$140.45	$140.50
Purchase #5	$141.30	3.264%	$145.912	$145.91	$145.90	$145.90
Purchase #6	$158.67	6.731%	$169.3501	$169.35	$169.35	$169.40
Purchase #7	$131.47	6.127%	$139.5252	$139.53	$139.55	$139.50
7 purchase totals =	$986.88		$1,063.3146	$1,063.32	$1,063.30	$1,063.40