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	$221.61	4.774%	$232.1897	$232.19	$232.20	$232.20
Purchase #2	$40.47	7.759%	$43.6101	$43.61	$43.60	$43.60
Purchase #3	$188.45	4.106%	$196.1878	$196.19	$196.20	$196.20
Purchase #4	$202.95	9.419%	$222.0659	$222.07	$222.05	$222.10
Purchase #5	$220.93	9.529%	$241.9824	$241.98	$242.00	$242.00
Purchase #6	$18.61	6.510%	$19.8215	$19.82	$19.80	$19.80
Purchase #7	$36.31	6.462%	$38.6564	$38.66	$38.65	$38.70
7 purchase totals =	$929.33		$994.5138	$994.52	$994.50	$994.60