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	$116.94	12.460%	$131.5107	$131.51	$131.50	$131.50
Purchase #2	$95.33	6.557%	$101.5808	$101.58	$101.60	$101.60
Purchase #3	$126.39	12.863%	$142.6475	$142.65	$142.65	$142.60
Purchase #4	$191.37	9.246%	$209.0641	$209.06	$209.05	$209.10
Purchase #5	$185.84	7.761%	$200.263	$200.26	$200.25	$200.30
Purchase #6	$171.31	8.131%	$185.2392	$185.24	$185.25	$185.20
Purchase #7	$180.36	12.595%	$203.0763	$203.08	$203.10	$203.10
7 purchase totals =	$1,067.54		$1,173.3816	$1,173.38	$1,173.40	$1,173.40