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	$83.96	13.346%	$95.1653	$95.17	$95.15	$95.20
Purchase #2	$53.61	10.513%	$59.246	$59.25	$59.25	$59.20
Purchase #3	$242.61	12.229%	$272.2788	$272.28	$272.30	$272.30
Purchase #4	$189.62	11.221%	$210.8973	$210.90	$210.90	$210.90
Purchase #5	$158.47	8.122%	$171.3409	$171.34	$171.35	$171.30
Purchase #6	$225.40	5.302%	$237.3507	$237.35	$237.35	$237.40
Purchase #7	$245.90	9.250%	$268.6458	$268.65	$268.65	$268.60
7 purchase totals =	$1,199.57		$1,314.9248	$1,314.94	$1,314.95	$1,314.90