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	$224.61	8.510%	$243.7243	$243.72	$243.70	$243.70
Purchase #2	$71.60	5.213%	$75.3325	$75.33	$75.35	$75.30
Purchase #3	$200.51	9.517%	$219.5925	$219.59	$219.60	$219.60
Purchase #4	$101.61	3.283%	$104.9459	$104.95	$104.95	$104.90
Purchase #5	$80.42	6.192%	$85.3996	$85.40	$85.40	$85.40
Purchase #6	$145.79	6.681%	$155.5302	$155.53	$155.55	$155.50
Purchase #7	$55.51	6.290%	$59.0016	$59.00	$59.00	$59.00
7 purchase totals =	$880.05		$943.5266	$943.52	$943.55	$943.40