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	$10.46	13.235%	$11.8444	$11.84	$11.85	$11.80
Purchase #2	$119.61	10.407%	$132.0578	$132.06	$132.05	$132.10
Purchase #3	$174.40	12.414%	$196.05	$196.05	$196.05	$196.10
Purchase #4	$146.44	3.593%	$151.7016	$151.70	$151.70	$151.70
Purchase #5	$209.36	4.494%	$218.7686	$218.77	$218.75	$218.80
Purchase #6	$240.62	3.287%	$248.5292	$248.53	$248.55	$248.50
Purchase #7	$103.71	3.685%	$107.5317	$107.53	$107.55	$107.50
7 purchase totals =	$1,004.60		$1,066.4833	$1,066.48	$1,066.50	$1,066.50