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	$112.33	6.168%	$119.2585	$119.26	$119.25	$119.30
Purchase #2	$176.69	13.107%	$199.8488	$199.85	$199.85	$199.80
Purchase #3	$192.73	6.319%	$204.9086	$204.91	$204.90	$204.90
Purchase #4	$133.50	5.630%	$141.0161	$141.02	$141.00	$141.00
Purchase #5	$160.38	7.788%	$172.8704	$172.87	$172.85	$172.90
Purchase #6	$195.55	10.662%	$216.3995	$216.40	$216.40	$216.40
Purchase #7	$139.64	9.288%	$152.6098	$152.61	$152.60	$152.60
7 purchase totals =	$1,110.82		$1,206.9117	$1,206.92	$1,206.85	$1,206.90