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	$86.50	7.715%	$93.1735	$93.17	$93.15	$93.20
Purchase #2	$86.95	10.438%	$96.0258	$96.03	$96.05	$96.00
Purchase #3	$78.47	13.312%	$88.9159	$88.92	$88.90	$88.90
Purchase #4	$19.77	13.821%	$22.5024	$22.50	$22.50	$22.50
Purchase #5	$6.52	11.545%	$7.2727	$7.27	$7.25	$7.30
Purchase #6	$47.56	12.736%	$53.6172	$53.62	$53.60	$53.60
Purchase #7	$98.87	13.165%	$111.8862	$111.89	$111.90	$111.90
7 purchase totals =	$424.64		$473.3937	$473.40	$473.35	$473.40