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	$91.44	3.230%	$94.3935	$94.39	$94.40	$94.40
Purchase #2	$168.41	4.852%	$176.5813	$176.58	$176.60	$176.60
Purchase #3	$75.45	9.805%	$82.8479	$82.85	$82.85	$82.80
Purchase #4	$38.93	4.529%	$40.6931	$40.69	$40.70	$40.70
Purchase #5	$216.95	13.605%	$246.466	$246.47	$246.45	$246.50
Purchase #6	$110.34	5.552%	$116.4661	$116.47	$116.45	$116.50
Purchase #7	$164.39	4.251%	$171.3782	$171.38	$171.40	$171.40
7 purchase totals =	$865.91		$928.8261	$928.83	$928.85	$928.90