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	$32.65	3.598%	$33.8247	$33.82	$33.80	$33.80
Purchase #2	$125.97	4.270%	$131.3489	$131.35	$131.35	$131.30
Purchase #3	$85.29	12.442%	$95.9018	$95.90	$95.90	$95.90
Purchase #4	$148.39	6.697%	$158.3277	$158.33	$158.35	$158.30
Purchase #5	$59.90	4.199%	$62.4152	$62.42	$62.40	$62.40
Purchase #6	$51.74	11.647%	$57.7662	$57.77	$57.75	$57.80
Purchase #7	$78.78	10.293%	$86.8888	$86.89	$86.90	$86.90
7 purchase totals =	$582.72		$626.4733	$626.48	$626.45	$626.40