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	$245.69	10.778%	$272.1705	$272.17	$272.15	$272.20
Purchase #2	$234.94	13.780%	$267.3147	$267.31	$267.30	$267.30
Purchase #3	$184.93	4.293%	$192.869	$192.87	$192.85	$192.90
Purchase #4	$39.42	3.430%	$40.7721	$40.77	$40.75	$40.80
Purchase #5	$121.78	12.815%	$137.3861	$137.39	$137.40	$137.40
Purchase #6	$245.50	5.243%	$258.3716	$258.37	$258.35	$258.40
Purchase #7	$18.51	8.601%	$20.102	$20.10	$20.10	$20.10
7 purchase totals =	$1,090.77		$1,188.9860	$1,188.98	$1,188.90	$1,189.10