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	$119.38	7.431%	$128.2511	$128.25	$128.25	$128.30
Purchase #2	$72.25	8.592%	$78.4577	$78.46	$78.45	$78.50
Purchase #3	$40.79	3.407%	$42.1797	$42.18	$42.20	$42.20
Purchase #4	$103.94	6.166%	$110.3489	$110.35	$110.35	$110.30
Purchase #5	$233.86	3.305%	$241.5891	$241.59	$241.60	$241.60
Purchase #6	$99.29	3.743%	$103.0064	$103.01	$103.00	$103.00
Purchase #7	$17.34	12.871%	$19.5718	$19.57	$19.55	$19.60
7 purchase totals =	$686.85		$723.4047	$723.41	$723.40	$723.50