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	$199.43	4.173%	$207.7522	$207.75	$207.75	$207.80
Purchase #2	$112.49	6.738%	$120.0696	$120.07	$120.05	$120.10
Purchase #3	$100.48	3.808%	$104.3063	$104.31	$104.30	$104.30
Purchase #4	$206.29	7.423%	$221.6029	$221.60	$221.60	$221.60
Purchase #5	$189.38	4.864%	$198.5914	$198.59	$198.60	$198.60
Purchase #6	$40.99	5.666%	$43.3125	$43.31	$43.30	$43.30
Purchase #7	$170.50	11.668%	$190.3939	$190.39	$190.40	$190.40
7 purchase totals =	$1,019.56		$1,086.0288	$1,086.02	$1,086.00	$1,086.10