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	$18.36	7.467%	$19.7309	$19.73	$19.75	$19.70
Purchase #2	$85.25	12.292%	$95.7289	$95.73	$95.75	$95.70
Purchase #3	$50.88	9.413%	$55.6693	$55.67	$55.65	$55.70
Purchase #4	$176.69	8.120%	$191.0372	$191.04	$191.05	$191.00
Purchase #5	$83.28	8.861%	$90.6594	$90.66	$90.65	$90.70
Purchase #6	$145.56	4.581%	$152.2281	$152.23	$152.25	$152.20
Purchase #7	$144.50	9.755%	$158.596	$158.60	$158.60	$158.60
7 purchase totals =	$704.52		$763.6498	$763.66	$763.70	$763.60