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	$224.26	13.831%	$255.2774	$255.28	$255.30	$255.30
Purchase #2	$133.91	11.333%	$149.086	$149.09	$149.10	$149.10
Purchase #3	$188.94	11.152%	$210.0106	$210.01	$210.00	$210.00
Purchase #4	$74.83	11.788%	$83.651	$83.65	$83.65	$83.70
Purchase #5	$135.41	11.433%	$150.8914	$150.89	$150.90	$150.90
Purchase #6	$146.43	6.741%	$156.3008	$156.30	$156.30	$156.30
Purchase #7	$69.81	5.637%	$73.7452	$73.75	$73.75	$73.70
7 purchase totals =	$973.59		$1,078.9624	$1,078.97	$1,079.00	$1,079.00