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	$111.75	6.699%	$119.2361	$119.24	$119.25	$119.20
Purchase #2	$241.64	6.480%	$257.2983	$257.30	$257.30	$257.30
Purchase #3	$130.81	12.151%	$146.7047	$146.70	$146.70	$146.70
Purchase #4	$91.86	9.472%	$100.561	$100.56	$100.55	$100.60
Purchase #5	$209.81	4.819%	$219.9207	$219.92	$219.90	$219.90
Purchase #6	$182.73	9.663%	$200.3872	$200.39	$200.40	$200.40
Purchase #7	$47.52	5.701%	$50.2291	$50.23	$50.25	$50.20
7 purchase totals =	$1,016.12		$1,094.3371	$1,094.34	$1,094.35	$1,094.30