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	$148.89	13.699%	$169.2864	$169.29	$169.30	$169.30
Purchase #2	$183.35	4.250%	$191.1424	$191.14	$191.15	$191.10
Purchase #3	$121.47	6.372%	$129.2101	$129.21	$129.20	$129.20
Purchase #4	$225.50	5.559%	$238.0355	$238.04	$238.05	$238.00
Purchase #5	$123.40	13.446%	$139.9924	$139.99	$140.00	$140.00
Purchase #6	$32.48	3.832%	$33.7246	$33.72	$33.70	$33.70
Purchase #7	$94.52	6.265%	$100.4417	$100.44	$100.45	$100.40
7 purchase totals =	$929.61		$1,001.8331	$1,001.83	$1,001.85	$1,001.70