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	$50.87	4.404%	$53.1103	$53.11	$53.10	$53.10
Purchase #2	$14.63	3.153%	$15.0913	$15.09	$15.10	$15.10
Purchase #3	$199.41	9.193%	$217.7418	$217.74	$217.75	$217.70
Purchase #4	$134.80	4.791%	$141.2583	$141.26	$141.25	$141.30
Purchase #5	$62.68	13.445%	$71.1073	$71.11	$71.10	$71.10
Purchase #6	$168.52	9.121%	$183.8907	$183.89	$183.90	$183.90
Purchase #7	$33.40	12.833%	$37.6862	$37.69	$37.70	$37.70
7 purchase totals =	$664.31		$719.8859	$719.89	$719.90	$719.90