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	$157.78	9.158%	$172.2295	$172.23	$172.25	$172.20
Purchase #2	$189.31	11.122%	$210.3651	$210.37	$210.35	$210.40
Purchase #3	$91.46	4.823%	$95.8711	$95.87	$95.85	$95.90
Purchase #4	$152.66	11.392%	$170.051	$170.05	$170.05	$170.10
Purchase #5	$25.32	10.119%	$27.8821	$27.88	$27.90	$27.90
Purchase #6	$64.65	3.664%	$67.0188	$67.02	$67.00	$67.00
Purchase #7	$112.64	9.686%	$123.5503	$123.55	$123.55	$123.60
7 purchase totals =	$793.82		$866.9679	$866.97	$866.95	$867.10