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	$171.72	12.821%	$193.7362	$193.74	$193.75	$193.70
Purchase #2	$151.60	4.399%	$158.2689	$158.27	$158.25	$158.30
Purchase #3	$248.30	8.768%	$270.0709	$270.07	$270.05	$270.10
Purchase #4	$59.97	13.185%	$67.877	$67.88	$67.90	$67.90
Purchase #5	$31.37	8.110%	$33.9141	$33.91	$33.90	$33.90
Purchase #6	$240.32	6.585%	$256.1451	$256.15	$256.15	$256.10
Purchase #7	$62.34	6.836%	$66.6016	$66.60	$66.60	$66.60
7 purchase totals =	$965.62		$1,046.6138	$1,046.62	$1,046.60	$1,046.60