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	$85.29	3.648%	$88.4014	$88.40	$88.40	$88.40
Purchase #2	$130.55	8.350%	$141.4509	$141.45	$141.45	$141.50
Purchase #3	$6.30	7.578%	$6.7774	$6.78	$6.80	$6.80
Purchase #4	$177.71	6.111%	$188.5699	$188.57	$188.55	$188.60
Purchase #5	$130.96	11.771%	$146.3753	$146.38	$146.40	$146.40
Purchase #6	$231.43	3.159%	$238.7409	$238.74	$238.75	$238.70
Purchase #7	$187.51	9.570%	$205.4547	$205.45	$205.45	$205.50
7 purchase totals =	$949.75		$1,015.7705	$1,015.77	$1,015.80	$1,015.90