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	$99.47	7.455%	$106.8855	$106.89	$106.90	$106.90
Purchase #2	$107.35	8.418%	$116.3867	$116.39	$116.40	$116.40
Purchase #3	$93.73	13.253%	$106.152	$106.15	$106.15	$106.20
Purchase #4	$57.95	11.456%	$64.5888	$64.59	$64.60	$64.60
Purchase #5	$126.55	3.557%	$131.0514	$131.05	$131.05	$131.10
Purchase #6	$32.62	10.300%	$35.9799	$35.98	$36.00	$36.00
Purchase #7	$248.74	9.797%	$273.1091	$273.11	$273.10	$273.10
7 purchase totals =	$766.41		$834.1534	$834.16	$834.20	$834.30