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	$59.66	4.453%	$62.3167	$62.32	$62.30	$62.30
Purchase #2	$141.28	5.328%	$148.8074	$148.81	$148.80	$148.80
Purchase #3	$195.58	11.821%	$218.6995	$218.70	$218.70	$218.70
Purchase #4	$123.33	5.518%	$130.1353	$130.14	$130.15	$130.10
Purchase #5	$98.68	12.756%	$111.2676	$111.27	$111.25	$111.30
Purchase #6	$227.51	13.807%	$258.9223	$258.92	$258.90	$258.90
Purchase #7	$36.29	10.293%	$40.0253	$40.03	$40.05	$40.00
7 purchase totals =	$882.33		$970.1741	$970.19	$970.15	$970.10