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	$25.61	4.529%	$26.7699	$26.77	$26.75	$26.80
Purchase #2	$60.85	11.516%	$67.8575	$67.86	$67.85	$67.90
Purchase #3	$119.28	4.192%	$124.2802	$124.28	$124.30	$124.30
Purchase #4	$233.45	13.290%	$264.4755	$264.48	$264.50	$264.50
Purchase #5	$10.39	7.558%	$11.1753	$11.18	$11.20	$11.20
Purchase #6	$43.27	7.676%	$46.5914	$46.59	$46.60	$46.60
Purchase #7	$179.64	6.612%	$191.5178	$191.52	$191.50	$191.50
7 purchase totals =	$672.49		$732.6676	$732.68	$732.70	$732.80