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	$242.25	13.581%	$275.15	$275.15	$275.15	$275.20
Purchase #2	$65.93	10.334%	$72.7432	$72.74	$72.75	$72.70
Purchase #3	$151.87	10.714%	$168.1414	$168.14	$168.15	$168.10
Purchase #4	$190.59	7.236%	$204.3811	$204.38	$204.40	$204.40
Purchase #5	$152.49	3.298%	$157.5191	$157.52	$157.50	$157.50
Purchase #6	$88.79	9.448%	$97.1789	$97.18	$97.20	$97.20
Purchase #7	$231.47	11.518%	$258.1307	$258.13	$258.15	$258.10
7 purchase totals =	$1,123.39		$1,233.2444	$1,233.24	$1,233.30	$1,233.20