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	$80.71	5.472%	$85.1265	$85.13	$85.15	$85.10
Purchase #2	$149.95	10.358%	$165.4818	$165.48	$165.50	$165.50
Purchase #3	$40.62	7.271%	$43.5735	$43.57	$43.55	$43.60
Purchase #4	$205.72	8.764%	$223.7493	$223.75	$223.75	$223.70
Purchase #5	$164.84	12.303%	$185.1203	$185.12	$185.10	$185.10
Purchase #6	$44.42	4.369%	$46.3607	$46.36	$46.35	$46.40
Purchase #7	$224.56	5.467%	$236.8367	$236.84	$236.85	$236.80
7 purchase totals =	$910.82		$986.2488	$986.25	$986.25	$986.20