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	$95.48	5.540%	$100.7696	$100.77	$100.75	$100.80
Purchase #2	$177.56	4.154%	$184.9358	$184.94	$184.95	$184.90
Purchase #3	$33.55	10.622%	$37.1137	$37.11	$37.10	$37.10
Purchase #4	$191.98	6.821%	$205.075	$205.08	$205.10	$205.10
Purchase #5	$154.96	10.394%	$171.0665	$171.07	$171.05	$171.10
Purchase #6	$123.70	10.300%	$136.4411	$136.44	$136.45	$136.40
Purchase #7	$53.47	6.788%	$57.0995	$57.10	$57.10	$57.10
7 purchase totals =	$830.70		$892.5012	$892.51	$892.50	$892.50