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	$52.60	12.444%	$59.1455	$59.15	$59.15	$59.10
Purchase #2	$117.79	9.665%	$129.1744	$129.17	$129.15	$129.20
Purchase #3	$83.89	12.128%	$94.0642	$94.06	$94.05	$94.10
Purchase #4	$131.60	8.665%	$143.0031	$143.00	$143.00	$143.00
Purchase #5	$67.67	6.781%	$72.2587	$72.26	$72.25	$72.30
Purchase #6	$174.83	11.740%	$195.355	$195.36	$195.35	$195.40
Purchase #7	$231.38	8.416%	$250.8529	$250.85	$250.85	$250.90
7 purchase totals =	$859.76		$943.8538	$943.85	$943.80	$944.00