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	$145.51	5.565%	$153.6076	$153.61	$153.60	$153.60
Purchase #2	$215.51	10.656%	$238.4747	$238.47	$238.45	$238.50
Purchase #3	$243.29	12.248%	$273.0882	$273.09	$273.10	$273.10
Purchase #4	$13.37	12.848%	$15.0878	$15.09	$15.10	$15.10
Purchase #5	$158.89	7.462%	$170.7464	$170.75	$170.75	$170.70
Purchase #6	$55.40	11.753%	$61.9112	$61.91	$61.90	$61.90
Purchase #7	$91.71	7.330%	$98.4323	$98.43	$98.45	$98.40
7 purchase totals =	$923.68		$1,011.3482	$1,011.35	$1,011.35	$1,011.30