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	$222.92	6.755%	$237.9782	$237.98	$238.00	$238.00
Purchase #2	$49.62	7.298%	$53.2413	$53.24	$53.25	$53.20
Purchase #3	$159.62	7.511%	$171.6091	$171.61	$171.60	$171.60
Purchase #4	$240.93	9.602%	$264.0641	$264.06	$264.05	$264.10
Purchase #5	$98.82	12.467%	$111.1399	$111.14	$111.15	$111.10
Purchase #6	$5.58	10.642%	$6.1738	$6.17	$6.15	$6.20
Purchase #7	$21.92	12.262%	$24.6078	$24.61	$24.60	$24.60
7 purchase totals =	$799.41		$868.8142	$868.81	$868.80	$868.80