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	$217.93	4.498%	$227.7325	$227.73	$227.75	$227.70
Purchase #2	$246.41	11.103%	$273.7689	$273.77	$273.75	$273.80
Purchase #3	$7.27	6.116%	$7.7146	$7.71	$7.70	$7.70
Purchase #4	$182.92	5.143%	$192.3276	$192.33	$192.35	$192.30
Purchase #5	$121.84	7.152%	$130.554	$130.55	$130.55	$130.60
Purchase #6	$91.29	10.796%	$101.1457	$101.15	$101.15	$101.10
Purchase #7	$76.29	9.116%	$83.2446	$83.24	$83.25	$83.20
7 purchase totals =	$943.95		$1,016.4879	$1,016.48	$1,016.50	$1,016.40