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	$130.45	5.823%	$138.0461	$138.05	$138.05	$138.00
Purchase #2	$103.38	6.354%	$109.9488	$109.95	$109.95	$109.90
Purchase #3	$200.89	10.200%	$221.3808	$221.38	$221.40	$221.40
Purchase #4	$81.43	11.666%	$90.9296	$90.93	$90.95	$90.90
Purchase #5	$225.30	4.230%	$234.8302	$234.83	$234.85	$234.80
Purchase #6	$234.56	8.751%	$255.0863	$255.09	$255.10	$255.10
Purchase #7	$69.91	9.872%	$76.8115	$76.81	$76.80	$76.80
7 purchase totals =	$1,045.92		$1,127.0333	$1,127.04	$1,127.10	$1,126.90