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	$73.25	12.828%	$82.6465	$82.65	$82.65	$82.60
Purchase #2	$111.80	11.420%	$124.5676	$124.57	$124.55	$124.60
Purchase #3	$61.77	13.496%	$70.1065	$70.11	$70.10	$70.10
Purchase #4	$172.86	3.274%	$178.5194	$178.52	$178.50	$178.50
Purchase #5	$193.97	10.116%	$213.592	$213.59	$213.60	$213.60
Purchase #6	$245.26	10.530%	$271.0859	$271.09	$271.10	$271.10
Purchase #7	$243.27	12.371%	$273.3649	$273.36	$273.35	$273.40
7 purchase totals =	$1,102.18		$1,213.8828	$1,213.89	$1,213.85	$1,213.90