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	$34.42	4.342%	$35.9145	$35.91	$35.90	$35.90
Purchase #2	$157.25	13.442%	$178.3875	$178.39	$178.40	$178.40
Purchase #3	$150.89	3.369%	$155.9735	$155.97	$155.95	$156.00
Purchase #4	$40.96	11.713%	$45.7576	$45.76	$45.75	$45.80
Purchase #5	$95.96	3.809%	$99.6151	$99.62	$99.60	$99.60
Purchase #6	$46.50	11.780%	$51.9777	$51.98	$52.00	$52.00
Purchase #7	$183.83	8.372%	$199.2202	$199.22	$199.20	$199.20
7 purchase totals =	$709.81		$766.8461	$766.85	$766.80	$766.90