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	$233.36	12.287%	$262.0329	$262.03	$262.05	$262.00
Purchase #2	$242.32	6.815%	$258.8341	$258.83	$258.85	$258.80
Purchase #3	$111.62	12.295%	$125.3437	$125.34	$125.35	$125.30
Purchase #4	$31.30	4.529%	$32.7176	$32.72	$32.70	$32.70
Purchase #5	$53.86	11.819%	$60.2257	$60.23	$60.25	$60.20
Purchase #6	$160.92	9.591%	$176.3538	$176.35	$176.35	$176.40
Purchase #7	$191.48	12.749%	$215.8918	$215.89	$215.90	$215.90
7 purchase totals =	$1,024.86		$1,131.3996	$1,131.39	$1,131.45	$1,131.30