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	$135.43	4.565%	$141.6124	$141.61	$141.60	$141.60
Purchase #2	$14.85	11.287%	$16.5261	$16.53	$16.55	$16.50
Purchase #3	$74.66	5.562%	$78.8126	$78.81	$78.80	$78.80
Purchase #4	$93.43	3.276%	$96.4908	$96.49	$96.50	$96.50
Purchase #5	$49.91	8.433%	$54.1189	$54.12	$54.10	$54.10
Purchase #6	$96.55	6.730%	$103.0478	$103.05	$103.05	$103.00
Purchase #7	$57.33	12.135%	$64.287	$64.29	$64.30	$64.30
7 purchase totals =	$522.16		$554.8956	$554.90	$554.90	$554.80