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	$198.92	9.399%	$217.6165	$217.62	$217.60	$217.60
Purchase #2	$88.58	11.165%	$98.47	$98.47	$98.45	$98.50
Purchase #3	$129.39	7.711%	$139.3673	$139.37	$139.35	$139.40
Purchase #4	$144.34	12.437%	$162.2916	$162.29	$162.30	$162.30
Purchase #5	$88.77	13.151%	$100.4441	$100.44	$100.45	$100.40
Purchase #6	$157.70	6.574%	$168.0672	$168.07	$168.05	$168.10
Purchase #7	$169.70	6.847%	$181.3194	$181.32	$181.30	$181.30
7 purchase totals =	$977.40		$1,067.5761	$1,067.58	$1,067.50	$1,067.60