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	$97.61	7.133%	$104.5725	$104.57	$104.55	$104.60
Purchase #2	$106.46	11.576%	$118.7838	$118.78	$118.80	$118.80
Purchase #3	$157.85	6.573%	$168.2255	$168.23	$168.25	$168.20
Purchase #4	$201.89	13.370%	$228.8827	$228.88	$228.90	$228.90
Purchase #5	$47.83	4.143%	$49.8116	$49.81	$49.80	$49.80
Purchase #6	$171.30	5.250%	$180.2933	$180.29	$180.30	$180.30
Purchase #7	$188.95	10.524%	$208.8351	$208.84	$208.85	$208.80
7 purchase totals =	$971.89		$1,059.4045	$1,059.40	$1,059.45	$1,059.40