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	$171.85	13.103%	$194.3675	$194.37	$194.35	$194.40
Purchase #2	$246.50	11.293%	$274.3372	$274.34	$274.35	$274.30
Purchase #3	$80.47	11.675%	$89.8649	$89.86	$89.85	$89.90
Purchase #4	$60.92	4.365%	$63.5792	$63.58	$63.60	$63.60
Purchase #5	$91.54	6.127%	$97.1487	$97.15	$97.15	$97.10
Purchase #6	$9.63	6.641%	$10.2695	$10.27	$10.25	$10.30
Purchase #7	$115.36	10.499%	$127.4716	$127.47	$127.45	$127.50
7 purchase totals =	$776.27		$857.0386	$857.04	$857.00	$857.10