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	$161.79	4.139%	$168.4865	$168.49	$168.50	$168.50
Purchase #2	$92.27	3.716%	$95.6988	$95.70	$95.70	$95.70
Purchase #3	$76.92	7.682%	$82.829	$82.83	$82.85	$82.80
Purchase #4	$47.79	6.785%	$51.0326	$51.03	$51.05	$51.00
Purchase #5	$139.92	9.754%	$153.5678	$153.57	$153.55	$153.60
Purchase #6	$38.88	10.301%	$42.885	$42.89	$42.90	$42.90
Purchase #7	$129.96	3.432%	$134.4202	$134.42	$134.40	$134.40
7 purchase totals =	$687.53		$728.9199	$728.93	$728.95	$728.90