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	$131.93	12.641%	$148.6073	$148.61	$148.60	$148.60
Purchase #2	$165.85	4.221%	$172.8505	$172.85	$172.85	$172.90
Purchase #3	$165.56	5.246%	$174.2453	$174.25	$174.25	$174.20
Purchase #4	$55.58	7.794%	$59.9119	$59.91	$59.90	$59.90
Purchase #5	$91.69	11.210%	$101.9684	$101.97	$101.95	$102.00
Purchase #6	$110.70	11.185%	$123.0818	$123.08	$123.10	$123.10
Purchase #7	$154.26	12.176%	$173.0427	$173.04	$173.05	$173.00
7 purchase totals =	$875.57		$953.7079	$953.71	$953.70	$953.70