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	$31.69	12.764%	$35.7349	$35.73	$35.75	$35.70
Purchase #2	$81.95	3.259%	$84.6208	$84.62	$84.60	$84.60
Purchase #3	$115.50	10.308%	$127.4057	$127.41	$127.40	$127.40
Purchase #4	$145.28	7.103%	$155.5992	$155.60	$155.60	$155.60
Purchase #5	$242.40	11.183%	$269.5076	$269.51	$269.50	$269.50
Purchase #6	$234.75	7.264%	$251.8022	$251.80	$251.80	$251.80
Purchase #7	$158.56	4.298%	$165.3749	$165.37	$165.35	$165.40
7 purchase totals =	$1,010.13		$1,090.0453	$1,090.04	$1,090.00	$1,090.00