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	$212.88	10.250%	$234.7002	$234.70	$234.70	$234.70
Purchase #2	$67.31	6.794%	$71.883	$71.88	$71.90	$71.90
Purchase #3	$39.73	13.743%	$45.1901	$45.19	$45.20	$45.20
Purchase #4	$89.59	11.217%	$99.6393	$99.64	$99.65	$99.60
Purchase #5	$53.99	5.728%	$57.0825	$57.08	$57.10	$57.10
Purchase #6	$176.53	7.460%	$189.6991	$189.70	$189.70	$189.70
Purchase #7	$20.43	6.304%	$21.7179	$21.72	$21.70	$21.70
7 purchase totals =	$660.46		$719.9121	$719.91	$719.95	$719.90