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	$95.83	8.566%	$104.0388	$104.04	$104.05	$104.00
Purchase #2	$166.93	12.638%	$188.0266	$188.03	$188.05	$188.00
Purchase #3	$119.55	6.556%	$127.3877	$127.39	$127.40	$127.40
Purchase #4	$56.86	5.330%	$59.8906	$59.89	$59.90	$59.90
Purchase #5	$226.68	11.740%	$253.2922	$253.29	$253.30	$253.30
Purchase #6	$167.25	12.686%	$188.4673	$188.47	$188.45	$188.50
Purchase #7	$66.88	7.403%	$71.8311	$71.83	$71.85	$71.80
7 purchase totals =	$899.98		$992.9343	$992.94	$993.00	$992.90