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	$131.92	4.192%	$137.4501	$137.45	$137.45	$137.50
Purchase #2	$53.45	7.365%	$57.3866	$57.39	$57.40	$57.40
Purchase #3	$97.35	13.527%	$110.5185	$110.52	$110.50	$110.50
Purchase #4	$109.83	7.345%	$117.897	$117.90	$117.90	$117.90
Purchase #5	$76.33	13.642%	$86.7429	$86.74	$86.75	$86.70
Purchase #6	$33.93	5.583%	$35.8243	$35.82	$35.80	$35.80
Purchase #7	$168.72	9.746%	$185.1635	$185.16	$185.15	$185.20
7 purchase totals =	$671.53		$730.9829	$730.98	$730.95	$731.00