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	$5.69	6.753%	$6.0742	$6.07	$6.05	$6.10
Purchase #2	$75.72	3.155%	$78.109	$78.11	$78.10	$78.10
Purchase #3	$26.25	5.468%	$27.6854	$27.69	$27.70	$27.70
Purchase #4	$86.92	9.626%	$95.2869	$95.29	$95.30	$95.30
Purchase #5	$139.92	9.778%	$153.6014	$153.60	$153.60	$153.60
Purchase #6	$13.96	12.847%	$15.7534	$15.75	$15.75	$15.80
Purchase #7	$205.76	13.510%	$233.5582	$233.56	$233.55	$233.60
7 purchase totals =	$554.22		$610.0685	$610.07	$610.05	$610.20