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	$78.39	5.684%	$82.8457	$82.85	$82.85	$82.80
Purchase #2	$170.70	11.492%	$190.3168	$190.32	$190.30	$190.30
Purchase #3	$82.43	12.442%	$92.6859	$92.69	$92.70	$92.70
Purchase #4	$197.96	11.671%	$221.0639	$221.06	$221.05	$221.10
Purchase #5	$211.59	6.272%	$224.8609	$224.86	$224.85	$224.90
Purchase #6	$37.65	5.575%	$39.749	$39.75	$39.75	$39.70
Purchase #7	$199.56	5.840%	$211.2143	$211.21	$211.20	$211.20
7 purchase totals =	$978.28		$1,062.7365	$1,062.74	$1,062.70	$1,062.70