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	$154.34	11.334%	$171.8329	$171.83	$171.85	$171.80
Purchase #2	$225.52	3.601%	$233.641	$233.64	$233.65	$233.60
Purchase #3	$126.44	9.820%	$138.8564	$138.86	$138.85	$138.90
Purchase #4	$120.25	13.840%	$136.8926	$136.89	$136.90	$136.90
Purchase #5	$72.67	10.839%	$80.5467	$80.55	$80.55	$80.50
Purchase #6	$225.30	4.857%	$236.2428	$236.24	$236.25	$236.20
Purchase #7	$136.95	13.303%	$155.1685	$155.17	$155.15	$155.20
7 purchase totals =	$1,061.47		$1,153.1809	$1,153.18	$1,153.20	$1,153.10