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	$142.88	3.347%	$147.6622	$147.66	$147.65	$147.70
Purchase #2	$131.61	8.571%	$142.8903	$142.89	$142.90	$142.90
Purchase #3	$237.28	10.629%	$262.5005	$262.50	$262.50	$262.50
Purchase #4	$219.65	9.522%	$240.5651	$240.57	$240.55	$240.60
Purchase #5	$43.39	4.847%	$45.4931	$45.49	$45.50	$45.50
Purchase #6	$209.39	6.453%	$222.9019	$222.90	$222.90	$222.90
Purchase #7	$84.36	13.661%	$95.8844	$95.88	$95.90	$95.90
7 purchase totals =	$1,068.56		$1,157.8975	$1,157.89	$1,157.90	$1,158.00