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	$149.45	12.318%	$167.8593	$167.86	$167.85	$167.90
Purchase #2	$216.30	7.320%	$232.1332	$232.13	$232.15	$232.10
Purchase #3	$33.34	3.721%	$34.5806	$34.58	$34.60	$34.60
Purchase #4	$223.68	13.434%	$253.7292	$253.73	$253.75	$253.70
Purchase #5	$55.35	8.258%	$59.9208	$59.92	$59.90	$59.90
Purchase #6	$218.72	3.564%	$226.5152	$226.52	$226.50	$226.50
Purchase #7	$30.25	11.492%	$33.7263	$33.73	$33.75	$33.70
7 purchase totals =	$927.09		$1,008.4646	$1,008.47	$1,008.50	$1,008.40