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	$249.41	5.211%	$262.4068	$262.41	$262.40	$262.40
Purchase #2	$41.28	13.519%	$46.8606	$46.86	$46.85	$46.90
Purchase #3	$171.43	7.655%	$184.553	$184.55	$184.55	$184.60
Purchase #4	$169.46	6.134%	$179.8547	$179.85	$179.85	$179.90
Purchase #5	$72.80	13.361%	$82.5268	$82.53	$82.55	$82.50
Purchase #6	$128.88	5.124%	$135.4838	$135.48	$135.50	$135.50
Purchase #7	$21.56	10.814%	$23.8915	$23.89	$23.90	$23.90
7 purchase totals =	$854.82		$915.5772	$915.57	$915.60	$915.70