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	$65.32	7.513%	$70.2275	$70.23	$70.25	$70.20
Purchase #2	$200.82	13.578%	$228.0873	$228.09	$228.10	$228.10
Purchase #3	$148.92	6.173%	$158.1128	$158.11	$158.10	$158.10
Purchase #4	$128.34	10.698%	$142.0698	$142.07	$142.05	$142.10
Purchase #5	$196.67	3.523%	$203.5987	$203.60	$203.60	$203.60
Purchase #6	$32.36	3.538%	$33.5049	$33.50	$33.50	$33.50
Purchase #7	$247.41	8.424%	$268.2518	$268.25	$268.25	$268.30
7 purchase totals =	$1,019.84		$1,103.8528	$1,103.85	$1,103.85	$1,103.90