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	$146.63	7.410%	$157.4953	$157.50	$157.50	$157.50
Purchase #2	$153.44	10.308%	$169.2566	$169.26	$169.25	$169.30
Purchase #3	$59.70	3.191%	$61.605	$61.61	$61.60	$61.60
Purchase #4	$170.26	12.724%	$191.9239	$191.92	$191.90	$191.90
Purchase #5	$245.66	8.229%	$265.8754	$265.88	$265.90	$265.90
Purchase #6	$98.78	12.396%	$111.0248	$111.02	$111.00	$111.00
Purchase #7	$140.63	5.789%	$148.7711	$148.77	$148.75	$148.80
7 purchase totals =	$1,015.10		$1,105.9521	$1,105.96	$1,105.90	$1,106.00