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	$184.47	6.468%	$196.4015	$196.40	$196.40	$196.40
Purchase #2	$177.63	6.462%	$189.1085	$189.11	$189.10	$189.10
Purchase #3	$70.59	11.232%	$78.5187	$78.52	$78.50	$78.50
Purchase #4	$59.83	10.374%	$66.0368	$66.04	$66.05	$66.00
Purchase #5	$245.29	8.430%	$265.9679	$265.97	$265.95	$266.00
Purchase #6	$213.30	7.632%	$229.5791	$229.58	$229.60	$229.60
Purchase #7	$140.42	11.667%	$156.8028	$156.80	$156.80	$156.80
7 purchase totals =	$1,091.53		$1,182.4153	$1,182.42	$1,182.40	$1,182.40