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	$92.47	3.257%	$95.4817	$95.48	$95.50	$95.50
Purchase #2	$152.93	10.167%	$168.4784	$168.48	$168.50	$168.50
Purchase #3	$120.30	7.182%	$128.9399	$128.94	$128.95	$128.90
Purchase #4	$27.73	3.278%	$28.639	$28.64	$28.65	$28.60
Purchase #5	$53.86	6.149%	$57.1719	$57.17	$57.15	$57.20
Purchase #6	$72.77	6.210%	$77.289	$77.29	$77.30	$77.30
Purchase #7	$11.38	11.162%	$12.6502	$12.65	$12.65	$12.70
7 purchase totals =	$531.44		$568.6501	$568.65	$568.70	$568.70