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	$182.31	4.647%	$190.7819	$190.78	$190.80	$190.80
Purchase #2	$127.93	12.621%	$144.076	$144.08	$144.10	$144.10
Purchase #3	$190.76	8.164%	$206.3336	$206.33	$206.35	$206.30
Purchase #4	$202.60	4.154%	$211.016	$211.02	$211.00	$211.00
Purchase #5	$227.40	12.779%	$256.4594	$256.46	$256.45	$256.50
Purchase #6	$102.89	8.365%	$111.4967	$111.50	$111.50	$111.50
Purchase #7	$228.60	11.258%	$254.3358	$254.34	$254.35	$254.30
7 purchase totals =	$1,262.49		$1,374.4994	$1,374.51	$1,374.55	$1,374.50