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	$103.65	7.568%	$111.4942	$111.49	$111.50	$111.50
Purchase #2	$111.33	5.832%	$117.8228	$117.82	$117.80	$117.80
Purchase #3	$157.94	5.816%	$167.1258	$167.13	$167.15	$167.10
Purchase #4	$80.43	8.804%	$87.5111	$87.51	$87.50	$87.50
Purchase #5	$182.37	9.112%	$198.9876	$198.99	$199.00	$199.00
Purchase #6	$199.81	8.516%	$216.8258	$216.83	$216.85	$216.80
Purchase #7	$174.94	6.258%	$185.8877	$185.89	$185.90	$185.90
7 purchase totals =	$1,010.47		$1,085.6550	$1,085.66	$1,085.70	$1,085.60