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	$191.51	10.226%	$211.0938	$211.09	$211.10	$211.10
Purchase #2	$105.99	5.189%	$111.4898	$111.49	$111.50	$111.50
Purchase #3	$147.91	6.130%	$156.9769	$156.98	$157.00	$157.00
Purchase #4	$158.89	5.661%	$167.8848	$167.88	$167.90	$167.90
Purchase #5	$33.61	4.533%	$35.1335	$35.13	$35.15	$35.10
Purchase #6	$104.30	7.500%	$112.1225	$112.12	$112.10	$112.10
Purchase #7	$20.31	6.584%	$21.6472	$21.65	$21.65	$21.60
7 purchase totals =	$762.52		$816.3485	$816.34	$816.40	$816.30