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	$11.40	4.103%	$11.8677	$11.87	$11.85	$11.90
Purchase #2	$118.46	4.558%	$123.8594	$123.86	$123.85	$123.90
Purchase #3	$57.77	8.125%	$62.4638	$62.46	$62.45	$62.50
Purchase #4	$5.69	3.664%	$5.8985	$5.90	$5.90	$5.90
Purchase #5	$249.53	5.416%	$263.0445	$263.04	$263.05	$263.00
Purchase #6	$86.25	3.475%	$89.2472	$89.25	$89.25	$89.20
Purchase #7	$142.30	11.687%	$158.9306	$158.93	$158.95	$158.90
7 purchase totals =	$671.40		$715.3117	$715.31	$715.30	$715.30