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	$94.49	11.256%	$105.1258	$105.13	$105.15	$105.10
Purchase #2	$74.50	12.308%	$83.6695	$83.67	$83.65	$83.70
Purchase #3	$106.79	9.864%	$117.3238	$117.32	$117.30	$117.30
Purchase #4	$114.26	6.323%	$121.4847	$121.48	$121.50	$121.50
Purchase #5	$212.96	4.434%	$222.4026	$222.40	$222.40	$222.40
Purchase #6	$51.80	5.227%	$54.5076	$54.51	$54.50	$54.50
Purchase #7	$86.64	4.721%	$90.7303	$90.73	$90.75	$90.70
7 purchase totals =	$741.44		$795.2443	$795.24	$795.25	$795.20