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	$84.28	7.403%	$90.5192	$90.52	$90.50	$90.50
Purchase #2	$235.26	13.558%	$267.1566	$267.16	$267.15	$267.20
Purchase #3	$59.40	6.130%	$63.0412	$63.04	$63.05	$63.00
Purchase #4	$214.48	3.742%	$222.5058	$222.51	$222.50	$222.50
Purchase #5	$152.26	11.542%	$169.8338	$169.83	$169.85	$169.80
Purchase #6	$54.60	11.280%	$60.7589	$60.76	$60.75	$60.80
Purchase #7	$123.40	13.312%	$139.827	$139.83	$139.85	$139.80
7 purchase totals =	$923.68		$1,013.6425	$1,013.65	$1,013.65	$1,013.60