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	$128.59	10.481%	$142.0675	$142.07	$142.05	$142.10
Purchase #2	$160.26	12.626%	$180.4944	$180.49	$180.50	$180.50
Purchase #3	$229.42	8.792%	$249.5906	$249.59	$249.60	$249.60
Purchase #4	$33.70	8.259%	$36.4833	$36.48	$36.50	$36.50
Purchase #5	$94.49	12.710%	$106.4997	$106.50	$106.50	$106.50
Purchase #6	$107.47	8.817%	$116.9456	$116.95	$116.95	$116.90
Purchase #7	$172.98	7.253%	$185.5262	$185.53	$185.55	$185.50
7 purchase totals =	$926.91		$1,017.6073	$1,017.61	$1,017.65	$1,017.60