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	$220.61	8.239%	$238.7861	$238.79	$238.80	$238.80
Purchase #2	$219.57	6.329%	$233.4666	$233.47	$233.45	$233.50
Purchase #3	$125.98	12.460%	$141.6771	$141.68	$141.70	$141.70
Purchase #4	$59.36	13.562%	$67.4104	$67.41	$67.40	$67.40
Purchase #5	$173.76	13.820%	$197.7736	$197.77	$197.75	$197.80
Purchase #6	$53.87	5.299%	$56.7246	$56.72	$56.70	$56.70
Purchase #7	$77.41	7.684%	$83.3582	$83.36	$83.35	$83.40
7 purchase totals =	$930.56		$1,019.1966	$1,019.20	$1,019.15	$1,019.30