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	$76.89	11.542%	$85.7646	$85.76	$85.75	$85.80
Purchase #2	$245.34	10.261%	$270.5143	$270.51	$270.50	$270.50
Purchase #3	$244.77	13.320%	$277.3734	$277.37	$277.35	$277.40
Purchase #4	$81.89	4.411%	$85.5022	$85.50	$85.50	$85.50
Purchase #5	$92.66	6.219%	$98.4225	$98.42	$98.40	$98.40
Purchase #6	$157.42	5.136%	$165.5051	$165.51	$165.50	$165.50
Purchase #7	$138.76	13.346%	$157.2789	$157.28	$157.30	$157.30
7 purchase totals =	$1,037.73		$1,140.3610	$1,140.35	$1,140.30	$1,140.40