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	$137.98	4.406%	$144.0594	$144.06	$144.05	$144.10
Purchase #2	$124.72	13.434%	$141.4749	$141.47	$141.45	$141.50
Purchase #3	$231.64	7.651%	$249.3628	$249.36	$249.35	$249.40
Purchase #4	$119.81	8.585%	$130.0957	$130.10	$130.10	$130.10
Purchase #5	$99.59	3.726%	$103.3007	$103.30	$103.30	$103.30
Purchase #6	$250.74	12.302%	$281.586	$281.59	$281.60	$281.60
Purchase #7	$139.25	9.858%	$152.9773	$152.98	$153.00	$153.00
7 purchase totals =	$1,103.73		$1,202.8568	$1,202.86	$1,202.85	$1,203.00