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	$116.63	10.166%	$128.4866	$128.49	$128.50	$128.50
Purchase #2	$24.33	11.644%	$27.163	$27.16	$27.15	$27.20
Purchase #3	$58.96	3.165%	$60.8261	$60.83	$60.85	$60.80
Purchase #4	$41.51	3.463%	$42.9475	$42.95	$42.95	$42.90
Purchase #5	$25.62	10.771%	$28.3795	$28.38	$28.40	$28.40
Purchase #6	$108.52	7.290%	$116.4311	$116.43	$116.45	$116.40
Purchase #7	$6.28	4.494%	$6.5622	$6.56	$6.55	$6.60
7 purchase totals =	$381.85		$410.7960	$410.80	$410.85	$410.80