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	$191.36	7.706%	$206.1062	$206.11	$206.10	$206.10
Purchase #2	$159.92	10.853%	$177.2761	$177.28	$177.30	$177.30
Purchase #3	$66.94	11.670%	$74.7519	$74.75	$74.75	$74.80
Purchase #4	$178.32	10.185%	$196.4819	$196.48	$196.50	$196.50
Purchase #5	$119.34	10.832%	$132.2669	$132.27	$132.25	$132.30
Purchase #6	$155.26	11.330%	$172.851	$172.85	$172.85	$172.90
Purchase #7	$72.96	7.473%	$78.4123	$78.41	$78.40	$78.40
7 purchase totals =	$944.10		$1,038.1463	$1,038.15	$1,038.15	$1,038.30