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	$243.90	4.872%	$255.7828	$255.78	$255.80	$255.80
Purchase #2	$79.82	7.598%	$85.8847	$85.88	$85.90	$85.90
Purchase #3	$29.25	6.561%	$31.1691	$31.17	$31.15	$31.20
Purchase #4	$229.92	3.482%	$237.9258	$237.93	$237.95	$237.90
Purchase #5	$173.43	13.174%	$196.2777	$196.28	$196.30	$196.30
Purchase #6	$13.39	3.373%	$13.8416	$13.84	$13.85	$13.80
Purchase #7	$106.83	12.874%	$120.5833	$120.58	$120.60	$120.60
7 purchase totals =	$876.54		$941.4650	$941.46	$941.55	$941.50