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	$71.87	9.495%	$78.6941	$78.69	$78.70	$78.70
Purchase #2	$118.83	11.322%	$132.2839	$132.28	$132.30	$132.30
Purchase #3	$240.78	5.803%	$254.7525	$254.75	$254.75	$254.80
Purchase #4	$78.63	13.235%	$89.0367	$89.04	$89.05	$89.00
Purchase #5	$98.27	8.643%	$106.7635	$106.76	$106.75	$106.80
Purchase #6	$141.91	4.836%	$148.7728	$148.77	$148.75	$148.80
Purchase #7	$247.93	9.129%	$270.5635	$270.56	$270.55	$270.60
7 purchase totals =	$998.22		$1,080.8670	$1,080.85	$1,080.85	$1,081.00