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	$139.87	9.153%	$152.6723	$152.67	$152.65	$152.70
Purchase #2	$59.69	8.869%	$64.9839	$64.98	$65.00	$65.00
Purchase #3	$196.72	9.670%	$215.7428	$215.74	$215.75	$215.70
Purchase #4	$105.57	5.729%	$111.6181	$111.62	$111.60	$111.60
Purchase #5	$230.48	6.122%	$244.59	$244.59	$244.60	$244.60
Purchase #6	$37.49	3.368%	$38.7527	$38.75	$38.75	$38.80
Purchase #7	$229.79	13.224%	$260.1774	$260.18	$260.20	$260.20
7 purchase totals =	$999.61		$1,088.5372	$1,088.53	$1,088.55	$1,088.60