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	$174.98	8.114%	$189.1779	$189.18	$189.20	$189.20
Purchase #2	$26.67	3.547%	$27.616	$27.62	$27.60	$27.60
Purchase #3	$147.84	11.270%	$164.5016	$164.50	$164.50	$164.50
Purchase #4	$37.55	10.453%	$41.4751	$41.48	$41.50	$41.50
Purchase #5	$82.37	9.852%	$90.4851	$90.49	$90.50	$90.50
Purchase #6	$217.62	7.394%	$233.7108	$233.71	$233.70	$233.70
Purchase #7	$9.28	11.421%	$10.3399	$10.34	$10.35	$10.30
7 purchase totals =	$696.31		$757.3064	$757.32	$757.35	$757.30