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	$68.87	3.716%	$71.4292	$71.43	$71.45	$71.40
Purchase #2	$56.87	8.669%	$61.8001	$61.80	$61.80	$61.80
Purchase #3	$68.92	13.655%	$78.331	$78.33	$78.35	$78.30
Purchase #4	$172.55	11.652%	$192.6555	$192.66	$192.65	$192.70
Purchase #5	$182.62	3.311%	$188.6665	$188.67	$188.65	$188.70
Purchase #6	$59.90	12.204%	$67.2102	$67.21	$67.20	$67.20
Purchase #7	$152.96	12.669%	$172.3385	$172.34	$172.35	$172.30
7 purchase totals =	$762.69		$832.4310	$832.44	$832.45	$832.40