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	$209.79	12.711%	$236.4564	$236.46	$236.45	$236.50
Purchase #2	$176.69	11.554%	$197.1048	$197.10	$197.10	$197.10
Purchase #3	$234.64	8.376%	$254.2934	$254.29	$254.30	$254.30
Purchase #4	$190.39	3.239%	$196.5567	$196.56	$196.55	$196.60
Purchase #5	$143.78	5.531%	$151.7325	$151.73	$151.75	$151.70
Purchase #6	$64.34	12.814%	$72.5845	$72.58	$72.60	$72.60
Purchase #7	$20.41	6.405%	$21.7173	$21.72	$21.70	$21.70
7 purchase totals =	$1,040.04		$1,130.4456	$1,130.44	$1,130.45	$1,130.50