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	$156.92	13.181%	$177.6036	$177.60	$177.60	$177.60
Purchase #2	$18.71	3.190%	$19.3068	$19.31	$19.30	$19.30
Purchase #3	$136.27	11.657%	$152.155	$152.16	$152.15	$152.20
Purchase #4	$34.38	7.650%	$37.0101	$37.01	$37.00	$37.00
Purchase #5	$184.31	3.291%	$190.3756	$190.38	$190.40	$190.40
Purchase #6	$227.89	6.261%	$242.1582	$242.16	$242.15	$242.20
Purchase #7	$113.89	7.471%	$122.3987	$122.40	$122.40	$122.40
7 purchase totals =	$872.37		$941.0080	$941.02	$941.00	$941.10