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	$11.30	5.566%	$11.929	$11.93	$11.95	$11.90
Purchase #2	$137.37	3.248%	$141.8318	$141.83	$141.85	$141.80
Purchase #3	$250.32	12.821%	$282.4135	$282.41	$282.40	$282.40
Purchase #4	$232.41	5.782%	$245.8479	$245.85	$245.85	$245.80
Purchase #5	$143.97	6.456%	$153.2647	$153.26	$153.25	$153.30
Purchase #6	$110.75	5.189%	$116.4968	$116.50	$116.50	$116.50
Purchase #7	$56.28	5.502%	$59.3765	$59.38	$59.40	$59.40
7 purchase totals =	$942.40		$1,011.1602	$1,011.16	$1,011.20	$1,011.10