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	$137.55	8.782%	$149.6296	$149.63	$149.65	$149.60
Purchase #2	$108.89	3.619%	$112.8307	$112.83	$112.85	$112.80
Purchase #3	$232.42	6.342%	$247.1601	$247.16	$247.15	$247.20
Purchase #4	$178.53	7.811%	$192.475	$192.48	$192.50	$192.50
Purchase #5	$134.97	3.532%	$139.7371	$139.74	$139.75	$139.70
Purchase #6	$76.94	7.168%	$82.4551	$82.46	$82.45	$82.50
Purchase #7	$78.34	12.495%	$88.1286	$88.13	$88.15	$88.10
7 purchase totals =	$947.64		$1,012.4162	$1,012.43	$1,012.50	$1,012.40