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	$116.57	13.298%	$132.0715	$132.07	$132.05	$132.10
Purchase #2	$234.41	4.227%	$244.3185	$244.32	$244.30	$244.30
Purchase #3	$190.94	4.361%	$199.2669	$199.27	$199.25	$199.30
Purchase #4	$162.38	3.802%	$168.5537	$168.55	$168.55	$168.60
Purchase #5	$43.83	5.851%	$46.3945	$46.39	$46.40	$46.40
Purchase #6	$160.98	9.158%	$175.7225	$175.72	$175.70	$175.70
Purchase #7	$140.48	11.572%	$156.7363	$156.74	$156.75	$156.70
7 purchase totals =	$1,049.59		$1,123.0639	$1,123.06	$1,123.00	$1,123.10