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	$21.28	4.793%	$22.3	$22.30	$22.30	$22.30
Purchase #2	$43.73	4.309%	$45.6143	$45.61	$45.60	$45.60
Purchase #3	$133.43	13.508%	$151.4537	$151.45	$151.45	$151.50
Purchase #4	$208.93	7.237%	$224.0503	$224.05	$224.05	$224.10
Purchase #5	$191.66	9.119%	$209.1375	$209.14	$209.15	$209.10
Purchase #6	$82.26	9.554%	$90.1191	$90.12	$90.10	$90.10
Purchase #7	$104.97	5.630%	$110.8798	$110.88	$110.90	$110.90
7 purchase totals =	$786.26		$853.5547	$853.55	$853.55	$853.60