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	$111.48	6.325%	$118.5311	$118.53	$118.55	$118.50
Purchase #2	$46.62	11.320%	$51.8974	$51.90	$51.90	$51.90
Purchase #3	$30.89	4.651%	$32.3267	$32.33	$32.35	$32.30
Purchase #4	$71.25	9.662%	$78.1342	$78.13	$78.15	$78.10
Purchase #5	$119.43	11.299%	$132.9244	$132.92	$132.90	$132.90
Purchase #6	$113.95	6.290%	$121.1175	$121.12	$121.10	$121.10
Purchase #7	$241.69	9.350%	$264.288	$264.29	$264.30	$264.30
7 purchase totals =	$735.31		$799.2193	$799.22	$799.25	$799.10