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	$183.79	13.210%	$208.0687	$208.07	$208.05	$208.10
Purchase #2	$56.72	8.218%	$61.3812	$61.38	$61.40	$61.40
Purchase #3	$194.83	7.112%	$208.6863	$208.69	$208.70	$208.70
Purchase #4	$54.37	9.164%	$59.3525	$59.35	$59.35	$59.40
Purchase #5	$58.45	10.161%	$64.3891	$64.39	$64.40	$64.40
Purchase #6	$12.44	11.578%	$13.8803	$13.88	$13.90	$13.90
Purchase #7	$57.89	8.243%	$62.6619	$62.66	$62.65	$62.70
7 purchase totals =	$618.49		$678.4200	$678.42	$678.45	$678.60