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	$174.58	11.408%	$194.4961	$194.50	$194.50	$194.50
Purchase #2	$64.39	10.430%	$71.1059	$71.11	$71.10	$71.10
Purchase #3	$29.25	9.705%	$32.0887	$32.09	$32.10	$32.10
Purchase #4	$22.71	5.719%	$24.0088	$24.01	$24.00	$24.00
Purchase #5	$102.88	13.110%	$116.3676	$116.37	$116.35	$116.40
Purchase #6	$164.69	13.315%	$186.6185	$186.62	$186.60	$186.60
Purchase #7	$101.83	9.234%	$111.233	$111.23	$111.25	$111.20
7 purchase totals =	$660.33		$735.9186	$735.93	$735.90	$735.90