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	$172.83	10.826%	$191.5406	$191.54	$191.55	$191.50
Purchase #2	$186.51	5.196%	$196.2011	$196.20	$196.20	$196.20
Purchase #3	$200.39	8.240%	$216.9021	$216.90	$216.90	$216.90
Purchase #4	$145.52	10.405%	$160.6614	$160.66	$160.65	$160.70
Purchase #5	$119.42	10.427%	$131.8719	$131.87	$131.85	$131.90
Purchase #6	$233.63	8.808%	$254.2081	$254.21	$254.20	$254.20
Purchase #7	$234.57	11.507%	$261.562	$261.56	$261.55	$261.60
7 purchase totals =	$1,292.87		$1,412.9472	$1,412.94	$1,412.90	$1,413.00