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	$116.91	11.401%	$130.2389	$130.24	$130.25	$130.20
Purchase #2	$173.40	12.374%	$194.8565	$194.86	$194.85	$194.90
Purchase #3	$53.98	5.114%	$56.7405	$56.74	$56.75	$56.70
Purchase #4	$242.62	9.205%	$264.9532	$264.95	$264.95	$265.00
Purchase #5	$60.25	11.385%	$67.1095	$67.11	$67.10	$67.10
Purchase #6	$227.68	5.801%	$240.8877	$240.89	$240.90	$240.90
Purchase #7	$43.30	10.321%	$47.769	$47.77	$47.75	$47.80
7 purchase totals =	$918.14		$1,002.5553	$1,002.56	$1,002.55	$1,002.60