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	$127.40	4.312%	$132.8935	$132.89	$132.90	$132.90
Purchase #2	$146.51	5.407%	$154.4318	$154.43	$154.45	$154.40
Purchase #3	$144.72	5.329%	$152.4321	$152.43	$152.45	$152.40
Purchase #4	$240.56	8.244%	$260.3918	$260.39	$260.40	$260.40
Purchase #5	$44.34	6.237%	$47.1055	$47.11	$47.10	$47.10
Purchase #6	$65.76	6.128%	$69.7898	$69.79	$69.80	$69.80
Purchase #7	$249.82	7.696%	$269.0461	$269.05	$269.05	$269.00
7 purchase totals =	$1,019.11		$1,086.0906	$1,086.09	$1,086.15	$1,086.00