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	$183.88	7.237%	$197.1874	$197.19	$197.20	$197.20
Purchase #2	$40.90	4.810%	$42.8673	$42.87	$42.85	$42.90
Purchase #3	$20.28	5.121%	$21.3185	$21.32	$21.30	$21.30
Purchase #4	$49.27	13.290%	$55.818	$55.82	$55.80	$55.80
Purchase #5	$110.72	3.265%	$114.335	$114.34	$114.35	$114.30
Purchase #6	$77.48	6.678%	$82.6541	$82.65	$82.65	$82.70
Purchase #7	$6.31	7.674%	$6.7942	$6.79	$6.80	$6.80
7 purchase totals =	$488.84		$520.9745	$520.98	$520.95	$521.00