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	$207.83	9.114%	$226.7716	$226.77	$226.75	$226.80
Purchase #2	$124.95	11.270%	$139.0319	$139.03	$139.05	$139.00
Purchase #3	$47.38	7.621%	$50.9908	$50.99	$51.00	$51.00
Purchase #4	$33.63	12.206%	$37.7349	$37.73	$37.75	$37.70
Purchase #5	$22.59	7.656%	$24.3195	$24.32	$24.30	$24.30
Purchase #6	$164.52	4.487%	$171.902	$171.90	$171.90	$171.90
Purchase #7	$86.78	4.617%	$90.7866	$90.79	$90.80	$90.80
7 purchase totals =	$687.68		$741.5373	$741.53	$741.55	$741.50