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	$57.99	11.128%	$64.4431	$64.44	$64.45	$64.40
Purchase #2	$69.36	10.551%	$76.6782	$76.68	$76.70	$76.70
Purchase #3	$224.78	8.815%	$244.5944	$244.59	$244.60	$244.60
Purchase #4	$56.59	9.309%	$61.858	$61.86	$61.85	$61.90
Purchase #5	$100.57	10.780%	$111.4114	$111.41	$111.40	$111.40
Purchase #6	$181.29	10.448%	$200.2312	$200.23	$200.25	$200.20
Purchase #7	$138.40	5.199%	$145.5954	$145.60	$145.60	$145.60
7 purchase totals =	$828.98		$904.8117	$904.81	$904.85	$904.80