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	$185.88	5.157%	$195.4658	$195.47	$195.45	$195.50
Purchase #2	$135.98	3.554%	$140.8127	$140.81	$140.80	$140.80
Purchase #3	$35.28	5.463%	$37.2073	$37.21	$37.20	$37.20
Purchase #4	$136.25	11.483%	$151.8956	$151.90	$151.90	$151.90
Purchase #5	$162.60	11.375%	$181.0958	$181.10	$181.10	$181.10
Purchase #6	$151.57	13.709%	$172.3487	$172.35	$172.35	$172.30
Purchase #7	$226.31	7.197%	$242.5975	$242.60	$242.60	$242.60
7 purchase totals =	$1,033.87		$1,121.4234	$1,121.44	$1,121.40	$1,121.40