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	$139.27	3.442%	$144.0637	$144.06	$144.05	$144.10
Purchase #2	$207.67	12.470%	$233.5664	$233.57	$233.55	$233.60
Purchase #3	$118.50	11.635%	$132.2875	$132.29	$132.30	$132.30
Purchase #4	$66.42	13.353%	$75.2891	$75.29	$75.30	$75.30
Purchase #5	$205.83	11.157%	$228.7945	$228.79	$228.80	$228.80
Purchase #6	$224.76	6.857%	$240.1718	$240.17	$240.15	$240.20
Purchase #7	$35.82	12.309%	$40.2291	$40.23	$40.25	$40.20
7 purchase totals =	$998.27		$1,094.4021	$1,094.40	$1,094.40	$1,094.50