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	$141.40	10.637%	$156.4407	$156.44	$156.45	$156.40
Purchase #2	$92.65	13.139%	$104.8233	$104.82	$104.80	$104.80
Purchase #3	$175.85	9.364%	$192.3166	$192.32	$192.30	$192.30
Purchase #4	$239.91	3.819%	$249.0722	$249.07	$249.05	$249.10
Purchase #5	$61.43	7.250%	$65.8837	$65.88	$65.90	$65.90
Purchase #6	$81.55	6.626%	$86.9535	$86.95	$86.95	$87.00
Purchase #7	$141.71	7.730%	$152.6642	$152.66	$152.65	$152.70
7 purchase totals =	$934.50		$1,008.1542	$1,008.14	$1,008.10	$1,008.20