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	$184.93	10.155%	$203.7096	$203.71	$203.70	$203.70
Purchase #2	$71.67	9.216%	$78.2751	$78.28	$78.30	$78.30
Purchase #3	$53.88	3.733%	$55.8913	$55.89	$55.90	$55.90
Purchase #4	$87.31	6.123%	$92.656	$92.66	$92.65	$92.70
Purchase #5	$140.95	5.639%	$148.8982	$148.90	$148.90	$148.90
Purchase #6	$174.67	10.798%	$193.5309	$193.53	$193.55	$193.50
Purchase #7	$26.87	6.294%	$28.5612	$28.56	$28.55	$28.60
7 purchase totals =	$740.28		$801.5223	$801.53	$801.55	$801.60