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	$33.64	4.201%	$35.0532	$35.05	$35.05	$35.10
Purchase #2	$55.33	4.552%	$57.8486	$57.85	$57.85	$57.80
Purchase #3	$218.28	6.108%	$231.6125	$231.61	$231.60	$231.60
Purchase #4	$209.75	5.561%	$221.4142	$221.41	$221.40	$221.40
Purchase #5	$227.25	7.736%	$244.8301	$244.83	$244.85	$244.80
Purchase #6	$184.56	3.170%	$190.4106	$190.41	$190.40	$190.40
Purchase #7	$95.44	6.270%	$101.4241	$101.42	$101.40	$101.40
7 purchase totals =	$1,024.25		$1,082.5933	$1,082.58	$1,082.55	$1,082.50