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	$206.75	4.292%	$215.6237	$215.62	$215.60	$215.60
Purchase #2	$89.45	5.446%	$94.3214	$94.32	$94.30	$94.30
Purchase #3	$182.27	7.317%	$195.6067	$195.61	$195.60	$195.60
Purchase #4	$93.50	12.552%	$105.2361	$105.24	$105.25	$105.20
Purchase #5	$241.92	13.794%	$275.2904	$275.29	$275.30	$275.30
Purchase #6	$115.60	11.537%	$128.9368	$128.94	$128.95	$128.90
Purchase #7	$13.62	11.673%	$15.2099	$15.21	$15.20	$15.20
7 purchase totals =	$943.11		$1,030.2250	$1,030.23	$1,030.20	$1,030.10