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	$74.79	10.841%	$82.898	$82.90	$82.90	$82.90
Purchase #2	$41.40	5.571%	$43.7064	$43.71	$43.70	$43.70
Purchase #3	$189.66	3.172%	$195.676	$195.68	$195.70	$195.70
Purchase #4	$91.81	13.175%	$103.906	$103.91	$103.90	$103.90
Purchase #5	$60.72	6.638%	$64.7506	$64.75	$64.75	$64.80
Purchase #6	$59.89	7.677%	$64.4878	$64.49	$64.50	$64.50
Purchase #7	$167.76	7.497%	$180.337	$180.34	$180.35	$180.30
7 purchase totals =	$686.03		$735.7618	$735.78	$735.80	$735.80