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	$164.47	8.635%	$178.672	$178.67	$178.65	$178.70
Purchase #2	$30.39	5.470%	$32.0523	$32.05	$32.05	$32.10
Purchase #3	$105.39	4.230%	$109.848	$109.85	$109.85	$109.80
Purchase #4	$216.52	3.308%	$223.6825	$223.68	$223.70	$223.70
Purchase #5	$35.81	4.413%	$37.3903	$37.39	$37.40	$37.40
Purchase #6	$11.86	10.137%	$13.0622	$13.06	$13.05	$13.10
Purchase #7	$231.67	4.871%	$242.9546	$242.95	$242.95	$243.00
7 purchase totals =	$796.11		$837.6619	$837.65	$837.65	$837.80