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	$69.76	5.444%	$73.5577	$73.56	$73.55	$73.60
Purchase #2	$33.66	12.392%	$37.8311	$37.83	$37.85	$37.80
Purchase #3	$79.84	7.293%	$85.6627	$85.66	$85.65	$85.70
Purchase #4	$250.55	9.283%	$273.8086	$273.81	$273.80	$273.80
Purchase #5	$66.70	8.782%	$72.5576	$72.56	$72.55	$72.60
Purchase #6	$66.41	9.139%	$72.4792	$72.48	$72.50	$72.50
Purchase #7	$145.97	8.703%	$158.6738	$158.67	$158.65	$158.70
7 purchase totals =	$712.89		$774.5707	$774.57	$774.55	$774.70