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	$149.83	7.129%	$160.5114	$160.51	$160.50	$160.50
Purchase #2	$153.69	12.706%	$173.2179	$173.22	$173.20	$173.20
Purchase #3	$194.43	8.721%	$211.3862	$211.39	$211.40	$211.40
Purchase #4	$95.31	7.406%	$102.3687	$102.37	$102.35	$102.40
Purchase #5	$139.32	6.841%	$148.8509	$148.85	$148.85	$148.90
Purchase #6	$110.55	11.611%	$123.386	$123.39	$123.40	$123.40
Purchase #7	$129.48	3.331%	$133.793	$133.79	$133.80	$133.80
7 purchase totals =	$972.61		$1,053.5141	$1,053.52	$1,053.50	$1,053.60