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	$38.59	4.768%	$40.43	$40.43	$40.45	$40.40
Purchase #2	$100.92	3.614%	$104.5672	$104.57	$104.55	$104.60
Purchase #3	$92.69	6.735%	$98.9327	$98.93	$98.95	$98.90
Purchase #4	$209.37	3.299%	$216.2771	$216.28	$216.30	$216.30
Purchase #5	$100.30	11.178%	$111.5115	$111.51	$111.50	$111.50
Purchase #6	$116.69	9.139%	$127.3543	$127.35	$127.35	$127.40
Purchase #7	$44.76	9.410%	$48.9719	$48.97	$48.95	$49.00
7 purchase totals =	$703.32		$748.0447	$748.04	$748.05	$748.10