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	$207.54	11.674%	$231.7682	$231.77	$231.75	$231.80
Purchase #2	$144.47	11.231%	$160.6954	$160.70	$160.70	$160.70
Purchase #3	$180.25	4.223%	$187.862	$187.86	$187.85	$187.90
Purchase #4	$45.89	10.564%	$50.7378	$50.74	$50.75	$50.70
Purchase #5	$36.83	8.733%	$40.0464	$40.05	$40.05	$40.00
Purchase #6	$250.50	9.122%	$273.3506	$273.35	$273.35	$273.40
Purchase #7	$174.43	4.835%	$182.8637	$182.86	$182.85	$182.90
7 purchase totals =	$1,039.91		$1,127.3241	$1,127.33	$1,127.30	$1,127.40