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	$81.36	8.253%	$88.0746	$88.07	$88.05	$88.10
Purchase #2	$214.46	8.838%	$233.414	$233.41	$233.40	$233.40
Purchase #3	$216.85	3.473%	$224.3812	$224.38	$224.40	$224.40
Purchase #4	$80.67	13.520%	$91.5766	$91.58	$91.60	$91.60
Purchase #5	$80.63	3.114%	$83.1408	$83.14	$83.15	$83.10
Purchase #6	$240.54	9.464%	$263.3047	$263.30	$263.30	$263.30
Purchase #7	$66.38	8.200%	$71.8232	$71.82	$71.80	$71.80
7 purchase totals =	$980.89		$1,055.7151	$1,055.70	$1,055.70	$1,055.70