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	$208.70	9.820%	$229.1943	$229.19	$229.20	$229.20
Purchase #2	$206.95	8.870%	$225.3065	$225.31	$225.30	$225.30
Purchase #3	$114.31	8.116%	$123.5874	$123.59	$123.60	$123.60
Purchase #4	$169.30	12.171%	$189.9055	$189.91	$189.90	$189.90
Purchase #5	$88.71	8.634%	$96.3692	$96.37	$96.35	$96.40
Purchase #6	$229.79	3.108%	$236.9319	$236.93	$236.95	$236.90
Purchase #7	$124.60	13.586%	$141.5282	$141.53	$141.55	$141.50
7 purchase totals =	$1,142.36		$1,242.8230	$1,242.83	$1,242.85	$1,242.80