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	$237.60	11.431%	$264.7601	$264.76	$264.75	$264.80
Purchase #2	$157.53	7.252%	$168.9541	$168.95	$168.95	$169.00
Purchase #3	$133.43	13.286%	$151.1575	$151.16	$151.15	$151.20
Purchase #4	$34.40	5.552%	$36.3099	$36.31	$36.30	$36.30
Purchase #5	$54.25	8.873%	$59.0636	$59.06	$59.05	$59.10
Purchase #6	$213.94	9.268%	$233.768	$233.77	$233.75	$233.80
Purchase #7	$58.83	9.296%	$64.2988	$64.30	$64.30	$64.30
7 purchase totals =	$889.98		$978.3120	$978.31	$978.25	$978.50