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	$56.48	5.197%	$59.4153	$59.42	$59.40	$59.40
Purchase #2	$102.76	6.215%	$109.1465	$109.15	$109.15	$109.10
Purchase #3	$192.76	6.554%	$205.3935	$205.39	$205.40	$205.40
Purchase #4	$62.86	6.639%	$67.0333	$67.03	$67.05	$67.00
Purchase #5	$7.56	6.329%	$8.0385	$8.04	$8.05	$8.00
Purchase #6	$121.80	13.235%	$137.9202	$137.92	$137.90	$137.90
Purchase #7	$13.52	6.486%	$14.3969	$14.40	$14.40	$14.40
7 purchase totals =	$557.74		$601.3442	$601.35	$601.35	$601.20