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	$178.56	8.614%	$193.9412	$193.94	$193.95	$193.90
Purchase #2	$239.42	8.321%	$259.3421	$259.34	$259.35	$259.30
Purchase #3	$100.44	4.728%	$105.1888	$105.19	$105.20	$105.20
Purchase #4	$35.96	4.269%	$37.4951	$37.50	$37.50	$37.50
Purchase #5	$34.83	4.583%	$36.4263	$36.43	$36.45	$36.40
Purchase #6	$226.71	6.122%	$240.5892	$240.59	$240.60	$240.60
Purchase #7	$52.60	5.793%	$55.6471	$55.65	$55.65	$55.60
7 purchase totals =	$868.52		$928.6298	$928.64	$928.70	$928.50