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	$175.72	9.536%	$192.4767	$192.48	$192.50	$192.50
Purchase #2	$215.70	13.781%	$245.4256	$245.43	$245.45	$245.40
Purchase #3	$46.39	10.242%	$51.1413	$51.14	$51.15	$51.10
Purchase #4	$211.68	6.512%	$225.4646	$225.46	$225.45	$225.50
Purchase #5	$73.70	6.718%	$78.6512	$78.65	$78.65	$78.70
Purchase #6	$8.91	13.690%	$10.1298	$10.13	$10.15	$10.10
Purchase #7	$189.80	5.134%	$199.5443	$199.54	$199.55	$199.50
7 purchase totals =	$921.90		$1,002.8335	$1,002.83	$1,002.90	$1,002.80