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	$144.76	4.118%	$150.7212	$150.72	$150.70	$150.70
Purchase #2	$92.29	8.236%	$99.891	$99.89	$99.90	$99.90
Purchase #3	$138.27	5.181%	$145.4338	$145.43	$145.45	$145.40
Purchase #4	$90.87	9.149%	$99.1837	$99.18	$99.20	$99.20
Purchase #5	$42.48	5.604%	$44.8606	$44.86	$44.85	$44.90
Purchase #6	$140.71	5.167%	$147.9805	$147.98	$148.00	$148.00
Purchase #7	$133.57	8.859%	$145.403	$145.40	$145.40	$145.40
7 purchase totals =	$782.95		$833.4738	$833.46	$833.50	$833.50