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	$117.91	12.710%	$132.8964	$132.90	$132.90	$132.90
Purchase #2	$134.53	7.625%	$144.7879	$144.79	$144.80	$144.80
Purchase #3	$136.66	10.405%	$150.8795	$150.88	$150.90	$150.90
Purchase #4	$84.27	3.389%	$87.1259	$87.13	$87.15	$87.10
Purchase #5	$40.58	4.147%	$42.2629	$42.26	$42.25	$42.30
Purchase #6	$170.59	11.695%	$190.5405	$190.54	$190.55	$190.50
Purchase #7	$230.76	13.410%	$261.7049	$261.70	$261.70	$261.70
7 purchase totals =	$915.30		$1,010.1980	$1,010.20	$1,010.25	$1,010.20