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	$116.47	10.122%	$128.2591	$128.26	$128.25	$128.30
Purchase #2	$19.69	8.337%	$21.3316	$21.33	$21.35	$21.30
Purchase #3	$245.35	4.135%	$255.4952	$255.50	$255.50	$255.50
Purchase #4	$222.89	5.145%	$234.3577	$234.36	$234.35	$234.40
Purchase #5	$210.69	9.745%	$231.2217	$231.22	$231.20	$231.20
Purchase #6	$240.89	6.392%	$256.2877	$256.29	$256.30	$256.30
Purchase #7	$86.97	3.864%	$90.3305	$90.33	$90.35	$90.30
7 purchase totals =	$1,142.95		$1,217.2835	$1,217.29	$1,217.30	$1,217.30