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	$59.30	3.844%	$61.5795	$61.58	$61.60	$61.60
Purchase #2	$241.56	6.200%	$256.5367	$256.54	$256.55	$256.50
Purchase #3	$72.89	11.377%	$81.1827	$81.18	$81.20	$81.20
Purchase #4	$188.91	12.361%	$212.2612	$212.26	$212.25	$212.30
Purchase #5	$210.34	11.370%	$234.2557	$234.26	$234.25	$234.30
Purchase #6	$86.53	4.851%	$90.7276	$90.73	$90.75	$90.70
Purchase #7	$34.37	5.162%	$36.1442	$36.14	$36.15	$36.10
7 purchase totals =	$893.90		$972.6876	$972.69	$972.75	$972.70