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	$209.30	6.484%	$222.871	$222.87	$222.85	$222.90
Purchase #2	$145.76	4.775%	$152.72	$152.72	$152.70	$152.70
Purchase #3	$152.72	4.401%	$159.4412	$159.44	$159.45	$159.40
Purchase #4	$117.76	11.684%	$131.5191	$131.52	$131.50	$131.50
Purchase #5	$225.48	3.492%	$233.3538	$233.35	$233.35	$233.40
Purchase #6	$69.99	4.140%	$72.8876	$72.89	$72.90	$72.90
Purchase #7	$146.39	11.115%	$162.6612	$162.66	$162.65	$162.70
7 purchase totals =	$1,067.40		$1,135.4539	$1,135.45	$1,135.40	$1,135.50