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	$177.29	6.501%	$188.8156	$188.82	$188.80	$188.80
Purchase #2	$145.51	7.165%	$155.9358	$155.94	$155.95	$155.90
Purchase #3	$84.66	5.197%	$89.0598	$89.06	$89.05	$89.10
Purchase #4	$64.26	4.790%	$67.3381	$67.34	$67.35	$67.30
Purchase #5	$75.60	8.223%	$81.8166	$81.82	$81.80	$81.80
Purchase #6	$226.84	8.513%	$246.1509	$246.15	$246.15	$246.20
Purchase #7	$200.34	11.506%	$223.3911	$223.39	$223.40	$223.40
7 purchase totals =	$974.50		$1,052.5079	$1,052.52	$1,052.50	$1,052.50