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	$190.46	9.272%	$208.1195	$208.12	$208.10	$208.10
Purchase #2	$37.69	13.343%	$42.719	$42.72	$42.70	$42.70
Purchase #3	$81.94	11.653%	$91.4885	$91.49	$91.50	$91.50
Purchase #4	$75.50	4.186%	$78.6604	$78.66	$78.65	$78.70
Purchase #5	$108.45	3.516%	$112.2631	$112.26	$112.25	$112.30
Purchase #6	$119.74	13.571%	$135.9899	$135.99	$136.00	$136.00
Purchase #7	$177.38	4.685%	$185.6903	$185.69	$185.70	$185.70
7 purchase totals =	$791.16		$854.9307	$854.93	$854.90	$855.00