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	$146.33	4.809%	$153.367	$153.37	$153.35	$153.40
Purchase #2	$185.48	3.122%	$191.2707	$191.27	$191.25	$191.30
Purchase #3	$49.56	10.750%	$54.8877	$54.89	$54.90	$54.90
Purchase #4	$104.61	10.798%	$115.9058	$115.91	$115.90	$115.90
Purchase #5	$85.58	4.185%	$89.1615	$89.16	$89.15	$89.20
Purchase #6	$90.70	5.660%	$95.8336	$95.83	$95.85	$95.80
Purchase #7	$249.55	12.207%	$280.0126	$280.01	$280.00	$280.00
7 purchase totals =	$911.81		$980.4389	$980.44	$980.40	$980.50