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	$149.33	10.782%	$165.4308	$165.43	$165.45	$165.40
Purchase #2	$80.89	6.287%	$85.9756	$85.98	$86.00	$86.00
Purchase #3	$73.67	9.834%	$80.9147	$80.91	$80.90	$80.90
Purchase #4	$88.85	7.441%	$95.4613	$95.46	$95.45	$95.50
Purchase #5	$131.51	11.301%	$146.3719	$146.37	$146.35	$146.40
Purchase #6	$93.32	4.499%	$97.5185	$97.52	$97.50	$97.50
Purchase #7	$36.84	10.869%	$40.8441	$40.84	$40.85	$40.80
7 purchase totals =	$654.41		$712.5169	$712.51	$712.50	$712.50