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	$150.82	13.749%	$171.5562	$171.56	$171.55	$171.60
Purchase #2	$40.72	5.280%	$42.87	$42.87	$42.85	$42.90
Purchase #3	$204.28	7.686%	$219.981	$219.98	$220.00	$220.00
Purchase #4	$28.30	4.324%	$29.5237	$29.52	$29.50	$29.50
Purchase #5	$221.69	9.468%	$242.6796	$242.68	$242.70	$242.70
Purchase #6	$132.80	3.246%	$137.1107	$137.11	$137.10	$137.10
Purchase #7	$242.34	7.830%	$261.3152	$261.32	$261.30	$261.30
7 purchase totals =	$1,020.95		$1,105.0364	$1,105.04	$1,105.00	$1,105.10