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	$113.87	3.282%	$117.6072	$117.61	$117.60	$117.60
Purchase #2	$127.46	11.102%	$141.6106	$141.61	$141.60	$141.60
Purchase #3	$29.62	13.151%	$33.5153	$33.52	$33.50	$33.50
Purchase #4	$130.44	4.861%	$136.7807	$136.78	$136.80	$136.80
Purchase #5	$74.73	3.102%	$77.0481	$77.05	$77.05	$77.00
Purchase #6	$221.38	10.151%	$243.8523	$243.85	$243.85	$243.90
Purchase #7	$43.51	4.361%	$45.4075	$45.41	$45.40	$45.40
7 purchase totals =	$741.01		$795.8217	$795.83	$795.80	$795.80