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	$185.74	3.861%	$192.9114	$192.91	$192.90	$192.90
Purchase #2	$62.89	13.433%	$71.338	$71.34	$71.35	$71.30
Purchase #3	$76.36	6.634%	$81.4257	$81.43	$81.45	$81.40
Purchase #4	$116.59	7.748%	$125.6234	$125.62	$125.60	$125.60
Purchase #5	$100.58	11.164%	$111.8088	$111.81	$111.80	$111.80
Purchase #6	$190.66	8.526%	$206.9157	$206.92	$206.90	$206.90
Purchase #7	$91.77	6.787%	$97.9984	$98.00	$98.00	$98.00
7 purchase totals =	$824.59		$888.0214	$888.03	$888.00	$887.90