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	$167.83	10.566%	$185.5629	$185.56	$185.55	$185.60
Purchase #2	$197.98	11.767%	$221.2763	$221.28	$221.30	$221.30
Purchase #3	$43.59	11.678%	$48.6804	$48.68	$48.70	$48.70
Purchase #4	$155.89	6.314%	$165.7329	$165.73	$165.75	$165.70
Purchase #5	$122.25	8.815%	$133.0263	$133.03	$133.05	$133.00
Purchase #6	$187.97	13.698%	$213.7181	$213.72	$213.70	$213.70
Purchase #7	$63.96	13.705%	$72.7257	$72.73	$72.75	$72.70
7 purchase totals =	$939.47		$1,040.7226	$1,040.73	$1,040.80	$1,040.70