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	$85.74	7.475%	$92.1491	$92.15	$92.15	$92.10
Purchase #2	$179.40	10.610%	$198.4343	$198.43	$198.45	$198.40
Purchase #3	$217.84	11.297%	$242.4494	$242.45	$242.45	$242.40
Purchase #4	$98.87	12.209%	$110.941	$110.94	$110.95	$110.90
Purchase #5	$53.73	10.552%	$59.3996	$59.40	$59.40	$59.40
Purchase #6	$74.57	8.425%	$80.8525	$80.85	$80.85	$80.90
Purchase #7	$145.39	4.474%	$151.8947	$151.89	$151.90	$151.90
7 purchase totals =	$855.54		$936.1206	$936.11	$936.15	$936.00