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	$167.37	9.605%	$183.4459	$183.45	$183.45	$183.40
Purchase #2	$13.96	13.365%	$15.8258	$15.83	$15.85	$15.80
Purchase #3	$165.52	9.800%	$181.741	$181.74	$181.75	$181.70
Purchase #4	$127.48	9.199%	$139.2069	$139.21	$139.20	$139.20
Purchase #5	$127.27	4.872%	$133.4706	$133.47	$133.45	$133.50
Purchase #6	$38.73	9.669%	$42.4748	$42.47	$42.45	$42.50
Purchase #7	$172.94	7.459%	$185.8396	$185.84	$185.85	$185.80
7 purchase totals =	$813.27		$882.0046	$882.01	$882.00	$881.90