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	$111.52	10.802%	$123.5664	$123.57	$123.55	$123.60
Purchase #2	$197.47	6.713%	$210.7262	$210.73	$210.75	$210.70
Purchase #3	$22.46	4.160%	$23.3943	$23.39	$23.40	$23.40
Purchase #4	$112.88	13.274%	$127.8637	$127.86	$127.85	$127.90
Purchase #5	$175.90	9.733%	$193.0203	$193.02	$193.00	$193.00
Purchase #6	$82.73	5.450%	$87.2388	$87.24	$87.25	$87.20
Purchase #7	$54.36	12.240%	$61.0137	$61.01	$61.00	$61.00
7 purchase totals =	$757.32		$826.8234	$826.82	$826.80	$826.80