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	$68.45	7.405%	$73.5187	$73.52	$73.50	$73.50
Purchase #2	$249.77	4.488%	$260.9797	$260.98	$261.00	$261.00
Purchase #3	$209.89	5.761%	$221.9818	$221.98	$222.00	$222.00
Purchase #4	$223.76	4.815%	$234.534	$234.53	$234.55	$234.50
Purchase #5	$71.79	12.580%	$80.8212	$80.82	$80.80	$80.80
Purchase #6	$150.93	13.606%	$171.4655	$171.47	$171.45	$171.50
Purchase #7	$174.83	13.837%	$199.0212	$199.02	$199.00	$199.00
7 purchase totals =	$1,149.42		$1,242.3221	$1,242.32	$1,242.30	$1,242.30