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	$210.91	12.799%	$237.9044	$237.90	$237.90	$237.90
Purchase #2	$59.97	10.279%	$66.1343	$66.13	$66.15	$66.10
Purchase #3	$15.27	12.311%	$17.1499	$17.15	$17.15	$17.10
Purchase #4	$217.65	7.209%	$233.3404	$233.34	$233.35	$233.30
Purchase #5	$80.41	11.502%	$89.6588	$89.66	$89.65	$89.70
Purchase #6	$173.43	11.216%	$192.8819	$192.88	$192.90	$192.90
Purchase #7	$237.33	5.545%	$250.4899	$250.49	$250.50	$250.50
7 purchase totals =	$994.97		$1,087.5596	$1,087.55	$1,087.60	$1,087.50