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	$209.47	6.818%	$223.7517	$223.75	$223.75	$223.80
Purchase #2	$137.54	3.576%	$142.4584	$142.46	$142.45	$142.50
Purchase #3	$66.98	13.814%	$76.2326	$76.23	$76.25	$76.20
Purchase #4	$76.56	4.246%	$79.8107	$79.81	$79.80	$79.80
Purchase #5	$81.72	7.133%	$87.5491	$87.55	$87.55	$87.50
Purchase #6	$246.63	7.292%	$264.6143	$264.61	$264.60	$264.60
Purchase #7	$210.38	5.645%	$222.256	$222.26	$222.25	$222.30
7 purchase totals =	$1,029.28		$1,096.6728	$1,096.67	$1,096.65	$1,096.70