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	$197.25	12.620%	$222.143	$222.14	$222.15	$222.10
Purchase #2	$32.44	13.161%	$36.7094	$36.71	$36.70	$36.70
Purchase #3	$34.27	10.604%	$37.904	$37.90	$37.90	$37.90
Purchase #4	$178.74	5.511%	$188.5904	$188.59	$188.60	$188.60
Purchase #5	$106.52	7.455%	$114.4611	$114.46	$114.45	$114.50
Purchase #6	$72.74	12.852%	$82.0885	$82.09	$82.10	$82.10
Purchase #7	$231.63	10.552%	$256.0716	$256.07	$256.05	$256.10
7 purchase totals =	$853.59		$937.9680	$937.96	$937.95	$938.00