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	$171.33	4.824%	$179.595	$179.60	$179.60	$179.60
Purchase #2	$111.35	6.661%	$118.767	$118.77	$118.75	$118.80
Purchase #3	$119.67	12.593%	$134.74	$134.74	$134.75	$134.70
Purchase #4	$111.39	4.227%	$116.0985	$116.10	$116.10	$116.10
Purchase #5	$19.48	4.724%	$20.4002	$20.40	$20.40	$20.40
Purchase #6	$201.80	4.296%	$210.4693	$210.47	$210.45	$210.50
Purchase #7	$148.95	13.350%	$168.8348	$168.83	$168.85	$168.80
7 purchase totals =	$883.97		$948.9048	$948.91	$948.90	$948.90