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	$242.63	13.542%	$275.487	$275.49	$275.50	$275.50
Purchase #2	$101.68	3.706%	$105.4483	$105.45	$105.45	$105.40
Purchase #3	$228.36	7.656%	$245.8432	$245.84	$245.85	$245.80
Purchase #4	$90.89	9.273%	$99.3182	$99.32	$99.30	$99.30
Purchase #5	$230.41	4.490%	$240.7554	$240.76	$240.75	$240.80
Purchase #6	$35.73	4.750%	$37.4272	$37.43	$37.45	$37.40
Purchase #7	$52.67	9.621%	$57.7374	$57.74	$57.75	$57.70
7 purchase totals =	$982.37		$1,062.0167	$1,062.03	$1,062.05	$1,061.90