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	$103.82	7.678%	$111.7913	$111.79	$111.80	$111.80
Purchase #2	$153.34	3.796%	$159.1608	$159.16	$159.15	$159.20
Purchase #3	$207.46	7.270%	$222.5423	$222.54	$222.55	$222.50
Purchase #4	$235.61	7.615%	$253.5517	$253.55	$253.55	$253.60
Purchase #5	$137.63	8.812%	$149.758	$149.76	$149.75	$149.80
Purchase #6	$62.84	12.192%	$70.5015	$70.50	$70.50	$70.50
Purchase #7	$36.62	10.298%	$40.3911	$40.39	$40.40	$40.40
7 purchase totals =	$937.32		$1,007.6967	$1,007.69	$1,007.70	$1,007.80