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	$103.53	7.640%	$111.4397	$111.44	$111.45	$111.40
Purchase #2	$102.67	10.209%	$113.1516	$113.15	$113.15	$113.20
Purchase #3	$125.54	4.324%	$130.9683	$130.97	$130.95	$131.00
Purchase #4	$187.60	4.542%	$196.1208	$196.12	$196.10	$196.10
Purchase #5	$50.76	11.244%	$56.4675	$56.47	$56.45	$56.50
Purchase #6	$90.94	9.447%	$99.5311	$99.53	$99.55	$99.50
Purchase #7	$197.79	9.261%	$216.1073	$216.11	$216.10	$216.10
7 purchase totals =	$858.83		$923.7863	$923.79	$923.75	$923.80