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	$95.70	6.519%	$101.9387	$101.94	$101.95	$101.90
Purchase #2	$222.30	9.127%	$242.5893	$242.59	$242.60	$242.60
Purchase #3	$239.59	12.771%	$270.188	$270.19	$270.20	$270.20
Purchase #4	$20.45	3.486%	$21.1629	$21.16	$21.15	$21.20
Purchase #5	$165.48	7.611%	$178.0747	$178.07	$178.05	$178.10
Purchase #6	$144.63	4.724%	$151.4623	$151.46	$151.45	$151.50
Purchase #7	$240.30	6.742%	$256.501	$256.50	$256.50	$256.50
7 purchase totals =	$1,128.45		$1,221.9169	$1,221.91	$1,221.90	$1,222.00