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	$126.58	3.109%	$130.5154	$130.52	$130.50	$130.50
Purchase #2	$222.60	7.149%	$238.5137	$238.51	$238.50	$238.50
Purchase #3	$92.61	6.486%	$98.6167	$98.62	$98.60	$98.60
Purchase #4	$98.52	11.458%	$109.8084	$109.81	$109.80	$109.80
Purchase #5	$148.51	12.597%	$167.2178	$167.22	$167.20	$167.20
Purchase #6	$37.43	9.858%	$41.1198	$41.12	$41.10	$41.10
Purchase #7	$230.76	5.227%	$242.8218	$242.82	$242.80	$242.80
7 purchase totals =	$957.01		$1,028.6136	$1,028.62	$1,028.50	$1,028.50