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	$11.96	5.664%	$12.6374	$12.64	$12.65	$12.60
Purchase #2	$176.70	8.131%	$191.0675	$191.07	$191.05	$191.10
Purchase #3	$96.74	9.166%	$105.6072	$105.61	$105.60	$105.60
Purchase #4	$103.64	7.419%	$111.3291	$111.33	$111.35	$111.30
Purchase #5	$29.35	13.431%	$33.292	$33.29	$33.30	$33.30
Purchase #6	$229.79	4.111%	$239.2367	$239.24	$239.25	$239.20
Purchase #7	$153.96	11.622%	$171.8532	$171.85	$171.85	$171.90
7 purchase totals =	$802.14		$865.0231	$865.03	$865.05	$865.00