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	$59.49	7.613%	$64.019	$64.02	$64.00	$64.00
Purchase #2	$33.46	6.679%	$35.6948	$35.69	$35.70	$35.70
Purchase #3	$137.86	9.234%	$150.59	$150.59	$150.60	$150.60
Purchase #4	$97.95	11.508%	$109.2221	$109.22	$109.20	$109.20
Purchase #5	$28.98	4.442%	$30.2673	$30.27	$30.25	$30.30
Purchase #6	$47.49	3.826%	$49.307	$49.31	$49.30	$49.30
Purchase #7	$203.79	11.692%	$227.6171	$227.62	$227.60	$227.60
7 purchase totals =	$609.02		$666.7173	$666.72	$666.65	$666.70