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	$250.30	4.484%	$261.5235	$261.52	$261.50	$261.50
Purchase #2	$124.53	13.295%	$141.0863	$141.09	$141.10	$141.10
Purchase #3	$70.40	8.386%	$76.3037	$76.30	$76.30	$76.30
Purchase #4	$80.37	6.587%	$85.664	$85.66	$85.65	$85.70
Purchase #5	$41.28	3.428%	$42.6951	$42.70	$42.70	$42.70
Purchase #6	$112.56	3.540%	$116.5446	$116.54	$116.55	$116.50
Purchase #7	$185.79	3.180%	$191.6981	$191.70	$191.70	$191.70
7 purchase totals =	$865.23		$915.5153	$915.51	$915.50	$915.50