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	$170.37	9.426%	$186.4291	$186.43	$186.45	$186.40
Purchase #2	$28.55	13.669%	$32.4525	$32.45	$32.45	$32.50
Purchase #3	$158.82	5.132%	$166.9706	$166.97	$166.95	$167.00
Purchase #4	$81.92	8.494%	$88.8783	$88.88	$88.90	$88.90
Purchase #5	$80.70	3.352%	$83.4051	$83.41	$83.40	$83.40
Purchase #6	$106.37	5.842%	$112.5841	$112.58	$112.60	$112.60
Purchase #7	$27.89	13.684%	$31.7065	$31.71	$31.70	$31.70
7 purchase totals =	$654.62		$702.4262	$702.43	$702.45	$702.50