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	$93.67	12.175%	$105.0743	$105.07	$105.05	$105.10
Purchase #2	$62.66	12.491%	$70.4869	$70.49	$70.50	$70.50
Purchase #3	$109.81	8.738%	$119.4052	$119.41	$119.40	$119.40
Purchase #4	$229.56	7.713%	$247.266	$247.27	$247.25	$247.30
Purchase #5	$215.39	12.150%	$241.5599	$241.56	$241.55	$241.60
Purchase #6	$135.33	3.570%	$140.1613	$140.16	$140.15	$140.20
Purchase #7	$128.75	12.633%	$145.015	$145.02	$145.00	$145.00
7 purchase totals =	$975.17		$1,068.9686	$1,068.98	$1,068.90	$1,069.10