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	$148.72	10.516%	$164.3594	$164.36	$164.35	$164.40
Purchase #2	$14.91	12.252%	$16.7368	$16.74	$16.75	$16.70
Purchase #3	$84.41	7.775%	$90.9729	$90.97	$90.95	$91.00
Purchase #4	$249.75	7.723%	$269.0382	$269.04	$269.05	$269.00
Purchase #5	$85.78	13.664%	$97.501	$97.50	$97.50	$97.50
Purchase #6	$56.59	5.636%	$59.7794	$59.78	$59.80	$59.80
Purchase #7	$40.73	11.866%	$45.563	$45.56	$45.55	$45.60
7 purchase totals =	$680.89		$743.9507	$743.95	$743.95	$744.00