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	$82.97	7.182%	$88.9289	$88.93	$88.95	$88.90
Purchase #2	$237.96	11.802%	$266.044	$266.04	$266.05	$266.00
Purchase #3	$145.57	4.267%	$151.7815	$151.78	$151.80	$151.80
Purchase #4	$228.70	12.491%	$257.2669	$257.27	$257.25	$257.30
Purchase #5	$40.93	5.392%	$43.1369	$43.14	$43.15	$43.10
Purchase #6	$192.58	13.786%	$219.1291	$219.13	$219.15	$219.10
Purchase #7	$161.63	5.135%	$169.9297	$169.93	$169.95	$169.90
7 purchase totals =	$1,090.34		$1,196.2170	$1,196.22	$1,196.30	$1,196.10