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	$234.45	5.508%	$247.3635	$247.36	$247.35	$247.40
Purchase #2	$245.56	4.538%	$256.7035	$256.70	$256.70	$256.70
Purchase #3	$205.34	13.812%	$233.7016	$233.70	$233.70	$233.70
Purchase #4	$19.42	7.557%	$20.8876	$20.89	$20.90	$20.90
Purchase #5	$108.79	3.782%	$112.9044	$112.90	$112.90	$112.90
Purchase #6	$33.48	8.217%	$36.2311	$36.23	$36.25	$36.20
Purchase #7	$49.27	9.818%	$54.1073	$54.11	$54.10	$54.10
7 purchase totals =	$896.31		$961.8990	$961.89	$961.90	$961.90