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	$212.38	9.757%	$233.1019	$233.10	$233.10	$233.10
Purchase #2	$98.50	8.679%	$107.0488	$107.05	$107.05	$107.00
Purchase #3	$88.56	13.312%	$100.3491	$100.35	$100.35	$100.30
Purchase #4	$134.72	13.450%	$152.8398	$152.84	$152.85	$152.80
Purchase #5	$203.27	11.552%	$226.7518	$226.75	$226.75	$226.80
Purchase #6	$38.38	11.249%	$42.6974	$42.70	$42.70	$42.70
Purchase #7	$85.98	4.169%	$89.5645	$89.56	$89.55	$89.60
7 purchase totals =	$861.79		$952.3533	$952.35	$952.35	$952.30