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	$41.42	11.700%	$46.2661	$46.27	$46.25	$46.30
Purchase #2	$34.98	7.470%	$37.593	$37.59	$37.60	$37.60
Purchase #3	$108.78	4.822%	$114.0254	$114.03	$114.05	$114.00
Purchase #4	$139.72	9.737%	$153.3245	$153.32	$153.30	$153.30
Purchase #5	$19.72	4.327%	$20.5733	$20.57	$20.55	$20.60
Purchase #6	$144.62	5.732%	$152.9096	$152.91	$152.90	$152.90
Purchase #7	$66.40	10.568%	$73.4172	$73.42	$73.40	$73.40
7 purchase totals =	$555.64		$598.1091	$598.11	$598.05	$598.10