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	$85.35	7.154%	$91.4559	$91.46	$91.45	$91.50
Purchase #2	$190.47	10.721%	$210.8903	$210.89	$210.90	$210.90
Purchase #3	$65.48	9.538%	$71.7255	$71.73	$71.75	$71.70
Purchase #4	$234.57	3.854%	$243.6103	$243.61	$243.60	$243.60
Purchase #5	$160.33	5.631%	$169.3582	$169.36	$169.35	$169.40
Purchase #6	$23.58	13.469%	$26.756	$26.76	$26.75	$26.80
Purchase #7	$240.26	3.114%	$247.7417	$247.74	$247.75	$247.70
7 purchase totals =	$1,000.04		$1,061.5379	$1,061.55	$1,061.55	$1,061.60