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	$199.31	11.390%	$222.0114	$222.01	$222.00	$222.00
Purchase #2	$52.65	13.430%	$59.7209	$59.72	$59.70	$59.70
Purchase #3	$100.89	9.350%	$110.3232	$110.32	$110.30	$110.30
Purchase #4	$131.94	11.167%	$146.6737	$146.67	$146.65	$146.70
Purchase #5	$84.88	13.651%	$96.467	$96.47	$96.45	$96.50
Purchase #6	$40.94	8.722%	$44.5108	$44.51	$44.50	$44.50
Purchase #7	$195.72	6.191%	$207.837	$207.84	$207.85	$207.80
7 purchase totals =	$806.33		$887.5440	$887.54	$887.45	$887.50