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	$79.74	11.752%	$89.111	$89.11	$89.10	$89.10
Purchase #2	$86.76	9.671%	$95.1506	$95.15	$95.15	$95.20
Purchase #3	$149.49	4.513%	$156.2365	$156.24	$156.25	$156.20
Purchase #4	$209.50	11.325%	$233.2259	$233.23	$233.25	$233.20
Purchase #5	$204.65	3.855%	$212.5393	$212.54	$212.55	$212.50
Purchase #6	$247.39	8.102%	$267.4335	$267.43	$267.45	$267.40
Purchase #7	$40.56	5.264%	$42.6951	$42.70	$42.70	$42.70
7 purchase totals =	$1,018.09		$1,096.3919	$1,096.40	$1,096.45	$1,096.30