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	$59.82	7.290%	$64.1809	$64.18	$64.20	$64.20
Purchase #2	$84.90	12.406%	$95.4327	$95.43	$95.45	$95.40
Purchase #3	$49.43	9.760%	$54.2544	$54.25	$54.25	$54.30
Purchase #4	$120.53	5.622%	$127.3062	$127.31	$127.30	$127.30
Purchase #5	$156.68	11.349%	$174.4616	$174.46	$174.45	$174.50
Purchase #6	$153.43	11.870%	$171.6421	$171.64	$171.65	$171.60
Purchase #7	$226.48	5.468%	$238.8639	$238.86	$238.85	$238.90
7 purchase totals =	$851.27		$926.1418	$926.13	$926.15	$926.20