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	$177.92	11.634%	$198.6192	$198.62	$198.60	$198.60
Purchase #2	$18.55	10.210%	$20.444	$20.44	$20.45	$20.40
Purchase #3	$85.84	7.859%	$92.5862	$92.59	$92.60	$92.60
Purchase #4	$211.67	5.425%	$223.1531	$223.15	$223.15	$223.20
Purchase #5	$201.29	7.245%	$215.8735	$215.87	$215.85	$215.90
Purchase #6	$241.70	11.807%	$270.2375	$270.24	$270.25	$270.20
Purchase #7	$129.86	9.263%	$141.8889	$141.89	$141.90	$141.90
7 purchase totals =	$1,066.83		$1,162.8024	$1,162.80	$1,162.80	$1,162.80