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	$216.94	3.211%	$223.9059	$223.91	$223.90	$223.90
Purchase #2	$97.81	11.492%	$109.0503	$109.05	$109.05	$109.10
Purchase #3	$67.77	3.703%	$70.2795	$70.28	$70.30	$70.30
Purchase #4	$158.37	8.796%	$172.3002	$172.30	$172.30	$172.30
Purchase #5	$243.67	5.397%	$256.8209	$256.82	$256.80	$256.80
Purchase #6	$201.25	3.540%	$208.3743	$208.37	$208.35	$208.40
Purchase #7	$44.88	11.801%	$50.1763	$50.18	$50.20	$50.20
7 purchase totals =	$1,030.69		$1,090.9074	$1,090.91	$1,090.90	$1,091.00