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	$153.75	3.781%	$159.5633	$159.56	$159.55	$159.60
Purchase #2	$211.56	5.203%	$222.5675	$222.57	$222.55	$222.60
Purchase #3	$67.40	4.358%	$70.3373	$70.34	$70.35	$70.30
Purchase #4	$24.95	11.642%	$27.8547	$27.85	$27.85	$27.90
Purchase #5	$64.32	6.622%	$68.5793	$68.58	$68.60	$68.60
Purchase #6	$161.31	5.665%	$170.4482	$170.45	$170.45	$170.40
Purchase #7	$32.38	9.676%	$35.5131	$35.51	$35.50	$35.50
7 purchase totals =	$715.67		$754.8634	$754.86	$754.85	$754.90