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	$210.78	5.665%	$222.7207	$222.72	$222.70	$222.70
Purchase #2	$52.34	13.746%	$59.5347	$59.53	$59.55	$59.50
Purchase #3	$242.54	4.227%	$252.7922	$252.79	$252.80	$252.80
Purchase #4	$228.43	7.579%	$245.7427	$245.74	$245.75	$245.70
Purchase #5	$38.26	11.462%	$42.6454	$42.65	$42.65	$42.60
Purchase #6	$104.44	3.710%	$108.3147	$108.31	$108.30	$108.30
Purchase #7	$188.95	6.238%	$200.7367	$200.74	$200.75	$200.70
7 purchase totals =	$1,065.74		$1,132.4871	$1,132.48	$1,132.50	$1,132.30