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	$228.27	4.278%	$238.0354	$238.04	$238.05	$238.00
Purchase #2	$12.75	11.551%	$14.2228	$14.22	$14.20	$14.20
Purchase #3	$211.71	7.644%	$227.8931	$227.89	$227.90	$227.90
Purchase #4	$240.46	13.802%	$273.6483	$273.65	$273.65	$273.60
Purchase #5	$63.57	11.177%	$70.6752	$70.68	$70.70	$70.70
Purchase #6	$152.78	7.626%	$164.431	$164.43	$164.45	$164.40
Purchase #7	$172.61	13.617%	$196.1143	$196.11	$196.10	$196.10
7 purchase totals =	$1,082.15		$1,185.0201	$1,185.02	$1,185.05	$1,184.90