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	$49.93	7.576%	$53.7127	$53.71	$53.70	$53.70
Purchase #2	$12.44	9.842%	$13.6643	$13.66	$13.65	$13.70
Purchase #3	$115.43	10.650%	$127.7233	$127.72	$127.70	$127.70
Purchase #4	$77.39	11.368%	$86.1877	$86.19	$86.20	$86.20
Purchase #5	$73.31	13.732%	$83.3769	$83.38	$83.40	$83.40
Purchase #6	$178.27	3.114%	$183.8213	$183.82	$183.80	$183.80
Purchase #7	$247.39	13.125%	$279.8599	$279.86	$279.85	$279.90
7 purchase totals =	$754.16		$828.3461	$828.34	$828.30	$828.40