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	$100.75	6.231%	$107.0277	$107.03	$107.05	$107.00
Purchase #2	$68.43	11.105%	$76.0292	$76.03	$76.05	$76.00
Purchase #3	$7.31	3.457%	$7.5627	$7.56	$7.55	$7.60
Purchase #4	$62.88	12.256%	$70.5866	$70.59	$70.60	$70.60
Purchase #5	$196.74	8.495%	$213.4531	$213.45	$213.45	$213.50
Purchase #6	$151.55	4.470%	$158.3243	$158.32	$158.30	$158.30
Purchase #7	$92.86	9.400%	$101.5888	$101.59	$101.60	$101.60
7 purchase totals =	$680.52		$734.5724	$734.57	$734.60	$734.60