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	$99.86	3.351%	$103.2063	$103.21	$103.20	$103.20
Purchase #2	$93.67	6.479%	$99.7389	$99.74	$99.75	$99.70
Purchase #3	$246.36	7.220%	$264.1472	$264.15	$264.15	$264.10
Purchase #4	$11.82	3.332%	$12.2138	$12.21	$12.20	$12.20
Purchase #5	$219.39	10.243%	$241.8621	$241.86	$241.85	$241.90
Purchase #6	$250.42	6.429%	$266.5195	$266.52	$266.50	$266.50
Purchase #7	$147.42	11.501%	$164.3748	$164.37	$164.35	$164.40
7 purchase totals =	$1,068.94		$1,152.0626	$1,152.06	$1,152.00	$1,152.00