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	$118.74	8.108%	$128.3674	$128.37	$128.35	$128.40
Purchase #2	$152.49	9.746%	$167.3517	$167.35	$167.35	$167.40
Purchase #3	$142.89	3.276%	$147.5711	$147.57	$147.55	$147.60
Purchase #4	$101.46	11.269%	$112.8935	$112.89	$112.90	$112.90
Purchase #5	$135.70	9.517%	$148.6146	$148.61	$148.60	$148.60
Purchase #6	$181.51	4.334%	$189.3766	$189.38	$189.40	$189.40
Purchase #7	$57.52	5.811%	$60.8625	$60.86	$60.85	$60.90
7 purchase totals =	$890.31		$955.0374	$955.03	$955.00	$955.20