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	$73.47	5.218%	$77.3037	$77.30	$77.30	$77.30
Purchase #2	$208.89	7.613%	$224.7928	$224.79	$224.80	$224.80
Purchase #3	$178.59	11.609%	$199.3225	$199.32	$199.30	$199.30
Purchase #4	$160.89	9.218%	$175.7208	$175.72	$175.70	$175.70
Purchase #5	$200.98	9.209%	$219.4882	$219.49	$219.50	$219.50
Purchase #6	$92.61	8.481%	$100.4643	$100.46	$100.45	$100.50
Purchase #7	$113.32	11.199%	$126.0107	$126.01	$126.00	$126.00
7 purchase totals =	$1,028.75		$1,123.1030	$1,123.09	$1,123.05	$1,123.10