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	$61.33	7.462%	$65.9064	$65.91	$65.90	$65.90
Purchase #2	$142.38	3.617%	$147.5299	$147.53	$147.55	$147.50
Purchase #3	$182.25	8.670%	$198.0511	$198.05	$198.05	$198.10
Purchase #4	$31.76	3.723%	$32.9424	$32.94	$32.95	$32.90
Purchase #5	$158.66	7.858%	$171.1275	$171.13	$171.15	$171.10
Purchase #6	$69.65	11.640%	$77.7573	$77.76	$77.75	$77.80
Purchase #7	$91.39	9.169%	$99.7695	$99.77	$99.75	$99.80
7 purchase totals =	$737.42		$793.0841	$793.09	$793.10	$793.10