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	$59.38	4.183%	$61.8639	$61.86	$61.85	$61.90
Purchase #2	$155.44	11.257%	$172.9379	$172.94	$172.95	$172.90
Purchase #3	$96.27	5.798%	$101.8517	$101.85	$101.85	$101.90
Purchase #4	$65.81	9.426%	$72.0133	$72.01	$72.00	$72.00
Purchase #5	$84.73	3.163%	$87.41	$87.41	$87.40	$87.40
Purchase #6	$235.31	3.507%	$243.5623	$243.56	$243.55	$243.60
Purchase #7	$43.50	11.758%	$48.6147	$48.61	$48.60	$48.60
7 purchase totals =	$740.44		$788.2538	$788.24	$788.20	$788.30