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	$95.83	9.767%	$105.1897	$105.19	$105.20	$105.20
Purchase #2	$39.97	9.530%	$43.7791	$43.78	$43.80	$43.80
Purchase #3	$30.61	3.380%	$31.6446	$31.64	$31.65	$31.60
Purchase #4	$222.42	12.374%	$249.9423	$249.94	$249.95	$249.90
Purchase #5	$99.58	10.219%	$109.7561	$109.76	$109.75	$109.80
Purchase #6	$115.54	12.464%	$129.9409	$129.94	$129.95	$129.90
Purchase #7	$227.40	12.299%	$255.3679	$255.37	$255.35	$255.40
7 purchase totals =	$831.35		$925.6206	$925.62	$925.65	$925.60