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	$196.26	6.139%	$208.3084	$208.31	$208.30	$208.30
Purchase #2	$128.32	12.478%	$144.3318	$144.33	$144.35	$144.30
Purchase #3	$205.55	7.423%	$220.808	$220.81	$220.80	$220.80
Purchase #4	$205.71	9.385%	$225.0159	$225.02	$225.00	$225.00
Purchase #5	$90.28	10.777%	$100.0095	$100.01	$100.00	$100.00
Purchase #6	$35.73	3.644%	$37.032	$37.03	$37.05	$37.00
Purchase #7	$92.59	7.576%	$99.6046	$99.60	$99.60	$99.60
7 purchase totals =	$954.44		$1,035.1102	$1,035.11	$1,035.10	$1,035.00