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	$63.41	13.526%	$71.9868	$71.99	$72.00	$72.00
Purchase #2	$137.61	11.615%	$153.5934	$153.59	$153.60	$153.60
Purchase #3	$139.77	12.681%	$157.4942	$157.49	$157.50	$157.50
Purchase #4	$123.27	5.575%	$130.1423	$130.14	$130.15	$130.10
Purchase #5	$209.74	12.311%	$235.5611	$235.56	$235.55	$235.60
Purchase #6	$166.69	4.297%	$173.8527	$173.85	$173.85	$173.90
Purchase #7	$59.97	4.801%	$62.8492	$62.85	$62.85	$62.80
7 purchase totals =	$900.46		$985.4797	$985.47	$985.50	$985.50