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	$14.60	8.416%	$15.8287	$15.83	$15.85	$15.80
Purchase #2	$129.76	9.451%	$142.0236	$142.02	$142.00	$142.00
Purchase #3	$151.40	10.485%	$167.2743	$167.27	$167.25	$167.30
Purchase #4	$59.61	13.308%	$67.5429	$67.54	$67.55	$67.50
Purchase #5	$92.55	11.625%	$103.3089	$103.31	$103.30	$103.30
Purchase #6	$151.40	12.133%	$169.7694	$169.77	$169.75	$169.80
Purchase #7	$103.55	12.762%	$116.7651	$116.77	$116.75	$116.80
7 purchase totals =	$702.87		$782.5129	$782.51	$782.45	$782.50