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	$124.31	11.865%	$139.0594	$139.06	$139.05	$139.10
Purchase #2	$235.99	13.579%	$268.0351	$268.04	$268.05	$268.00
Purchase #3	$167.63	13.687%	$190.5735	$190.57	$190.55	$190.60
Purchase #4	$148.90	4.691%	$155.8849	$155.88	$155.90	$155.90
Purchase #5	$106.89	11.480%	$119.161	$119.16	$119.15	$119.20
Purchase #6	$115.58	10.545%	$127.7679	$127.77	$127.75	$127.80
Purchase #7	$106.90	4.678%	$111.9008	$111.90	$111.90	$111.90
7 purchase totals =	$1,006.20		$1,112.3826	$1,112.38	$1,112.35	$1,112.50