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	$185.46	13.290%	$210.1076	$210.11	$210.10	$210.10
Purchase #2	$198.74	5.327%	$209.3269	$209.33	$209.35	$209.30
Purchase #3	$112.33	6.713%	$119.8707	$119.87	$119.85	$119.90
Purchase #4	$87.58	10.837%	$97.071	$97.07	$97.05	$97.10
Purchase #5	$175.96	11.679%	$196.5104	$196.51	$196.50	$196.50
Purchase #6	$180.93	10.873%	$200.6025	$200.60	$200.60	$200.60
Purchase #7	$240.78	8.568%	$261.41	$261.41	$261.40	$261.40
7 purchase totals =	$1,181.78		$1,294.8991	$1,294.90	$1,294.85	$1,294.90