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	$89.72	5.333%	$94.5048	$94.50	$94.50	$94.50
Purchase #2	$30.59	8.758%	$33.2691	$33.27	$33.25	$33.30
Purchase #3	$118.93	4.158%	$123.8751	$123.88	$123.90	$123.90
Purchase #4	$143.73	5.181%	$151.1767	$151.18	$151.20	$151.20
Purchase #5	$68.82	11.333%	$76.6194	$76.62	$76.60	$76.60
Purchase #6	$157.56	6.490%	$167.7856	$167.79	$167.80	$167.80
Purchase #7	$123.59	11.643%	$137.9796	$137.98	$138.00	$138.00
7 purchase totals =	$732.94		$785.2103	$785.22	$785.25	$785.30