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	$227.64	10.562%	$251.6833	$251.68	$251.70	$251.70
Purchase #2	$34.83	4.386%	$36.3576	$36.36	$36.35	$36.40
Purchase #3	$31.88	3.695%	$33.058	$33.06	$33.05	$33.10
Purchase #4	$13.25	4.331%	$13.8239	$13.82	$13.80	$13.80
Purchase #5	$62.29	3.294%	$64.3418	$64.34	$64.35	$64.30
Purchase #6	$41.31	3.699%	$42.8381	$42.84	$42.85	$42.80
Purchase #7	$38.90	8.153%	$42.0715	$42.07	$42.05	$42.10
7 purchase totals =	$450.10		$484.1742	$484.17	$484.15	$484.20