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	$245.33	6.496%	$261.2666	$261.27	$261.25	$261.30
Purchase #2	$108.82	4.389%	$113.5961	$113.60	$113.60	$113.60
Purchase #3	$183.73	5.297%	$193.4622	$193.46	$193.45	$193.50
Purchase #4	$32.53	3.287%	$33.5993	$33.60	$33.60	$33.60
Purchase #5	$179.82	4.565%	$188.0288	$188.03	$188.05	$188.00
Purchase #6	$117.33	6.118%	$124.5082	$124.51	$124.50	$124.50
Purchase #7	$232.68	13.842%	$264.8876	$264.89	$264.90	$264.90
7 purchase totals =	$1,100.24		$1,179.3488	$1,179.36	$1,179.35	$1,179.40