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	$231.62	4.408%	$241.8298	$241.83	$241.85	$241.80
Purchase #2	$19.90	8.821%	$21.6554	$21.66	$21.65	$21.70
Purchase #3	$66.83	8.318%	$72.3889	$72.39	$72.40	$72.40
Purchase #4	$82.84	6.558%	$88.2726	$88.27	$88.25	$88.30
Purchase #5	$131.92	11.447%	$147.0209	$147.02	$147.00	$147.00
Purchase #6	$61.74	6.541%	$65.7784	$65.78	$65.80	$65.80
Purchase #7	$46.88	5.286%	$49.3581	$49.36	$49.35	$49.40
7 purchase totals =	$641.73		$686.3041	$686.31	$686.30	$686.40