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	$54.60	8.816%	$59.4135	$59.41	$59.40	$59.40
Purchase #2	$239.98	4.560%	$250.9231	$250.92	$250.90	$250.90
Purchase #3	$32.76	12.476%	$36.8471	$36.85	$36.85	$36.80
Purchase #4	$242.74	9.194%	$265.0575	$265.06	$265.05	$265.10
Purchase #5	$112.37	5.321%	$118.3492	$118.35	$118.35	$118.30
Purchase #6	$154.92	9.142%	$169.0828	$169.08	$169.10	$169.10
Purchase #7	$104.55	12.186%	$117.2905	$117.29	$117.30	$117.30
7 purchase totals =	$941.92		$1,016.9637	$1,016.96	$1,016.95	$1,016.90