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	$127.94	10.558%	$141.4479	$141.45	$141.45	$141.40
Purchase #2	$51.70	10.327%	$57.0391	$57.04	$57.05	$57.00
Purchase #3	$208.53	9.585%	$228.5176	$228.52	$228.50	$228.50
Purchase #4	$131.62	11.343%	$146.5497	$146.55	$146.55	$146.50
Purchase #5	$148.65	12.484%	$167.2075	$167.21	$167.20	$167.20
Purchase #6	$191.39	9.647%	$209.8534	$209.85	$209.85	$209.90
Purchase #7	$125.53	3.787%	$130.2838	$130.28	$130.30	$130.30
7 purchase totals =	$985.36		$1,080.8990	$1,080.90	$1,080.90	$1,080.80