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	$181.41	7.192%	$194.457	$194.46	$194.45	$194.50
Purchase #2	$192.48	12.175%	$215.9144	$215.91	$215.90	$215.90
Purchase #3	$30.85	5.752%	$32.6245	$32.62	$32.60	$32.60
Purchase #4	$83.91	6.479%	$89.3465	$89.35	$89.35	$89.30
Purchase #5	$110.50	13.204%	$125.0904	$125.09	$125.10	$125.10
Purchase #6	$48.42	5.145%	$50.9112	$50.91	$50.90	$50.90
Purchase #7	$166.90	8.187%	$180.5641	$180.56	$180.55	$180.60
7 purchase totals =	$814.47		$888.9081	$888.90	$888.85	$888.90