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	$84.48	5.718%	$89.3106	$89.31	$89.30	$89.30
Purchase #2	$163.29	4.809%	$171.1426	$171.14	$171.15	$171.10
Purchase #3	$57.30	4.133%	$59.6682	$59.67	$59.65	$59.70
Purchase #4	$11.69	11.265%	$13.0069	$13.01	$13.00	$13.00
Purchase #5	$208.52	9.448%	$228.221	$228.22	$228.20	$228.20
Purchase #6	$173.51	5.162%	$182.4666	$182.47	$182.45	$182.50
Purchase #7	$237.62	12.827%	$268.0995	$268.10	$268.10	$268.10
7 purchase totals =	$936.41		$1,011.9154	$1,011.92	$1,011.85	$1,011.90