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	$96.27	7.432%	$103.4248	$103.42	$103.40	$103.40
Purchase #2	$35.80	13.112%	$40.4941	$40.49	$40.50	$40.50
Purchase #3	$18.32	7.518%	$19.6973	$19.70	$19.70	$19.70
Purchase #4	$164.53	3.260%	$169.8937	$169.89	$169.90	$169.90
Purchase #5	$65.98	8.270%	$71.4365	$71.44	$71.45	$71.40
Purchase #6	$152.94	10.249%	$168.6148	$168.61	$168.60	$168.60
Purchase #7	$161.85	6.335%	$172.1032	$172.10	$172.10	$172.10
7 purchase totals =	$695.69		$745.6644	$745.65	$745.65	$745.60