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	$185.71	5.601%	$196.1116	$196.11	$196.10	$196.10
Purchase #2	$50.99	11.475%	$56.8411	$56.84	$56.85	$56.80
Purchase #3	$154.34	6.744%	$164.7487	$164.75	$164.75	$164.70
Purchase #4	$244.30	5.665%	$258.1396	$258.14	$258.15	$258.10
Purchase #5	$190.38	9.791%	$209.0201	$209.02	$209.00	$209.00
Purchase #6	$191.67	8.232%	$207.4483	$207.45	$207.45	$207.40
Purchase #7	$52.29	13.602%	$59.4025	$59.40	$59.40	$59.40
7 purchase totals =	$1,069.68		$1,151.7119	$1,151.71	$1,151.70	$1,151.50