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	$190.93	4.811%	$200.1156	$200.12	$200.10	$200.10
Purchase #2	$165.82	6.430%	$176.4822	$176.48	$176.50	$176.50
Purchase #3	$50.56	6.673%	$53.9339	$53.93	$53.95	$53.90
Purchase #4	$128.73	8.481%	$139.6476	$139.65	$139.65	$139.60
Purchase #5	$82.87	7.860%	$89.3836	$89.38	$89.40	$89.40
Purchase #6	$11.38	6.836%	$12.1579	$12.16	$12.15	$12.20
Purchase #7	$222.99	11.769%	$249.2337	$249.23	$249.25	$249.20
7 purchase totals =	$853.28		$920.9545	$920.95	$921.00	$920.90