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	$95.44	6.583%	$101.7228	$101.72	$101.70	$101.70
Purchase #2	$131.71	8.686%	$143.1503	$143.15	$143.15	$143.20
Purchase #3	$216.63	13.479%	$245.8296	$245.83	$245.85	$245.80
Purchase #4	$181.96	5.869%	$192.6392	$192.64	$192.65	$192.60
Purchase #5	$118.27	11.466%	$131.8308	$131.83	$131.85	$131.80
Purchase #6	$97.95	6.114%	$103.9387	$103.94	$103.95	$103.90
Purchase #7	$159.67	5.364%	$168.2347	$168.23	$168.25	$168.20
7 purchase totals =	$1,001.63		$1,087.3461	$1,087.34	$1,087.40	$1,087.20