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	$40.49	13.624%	$46.0064	$46.01	$46.00	$46.00
Purchase #2	$85.58	10.303%	$94.3973	$94.40	$94.40	$94.40
Purchase #3	$111.61	3.700%	$115.7396	$115.74	$115.75	$115.70
Purchase #4	$86.59	9.581%	$94.8862	$94.89	$94.90	$94.90
Purchase #5	$207.88	8.534%	$225.6205	$225.62	$225.60	$225.60
Purchase #6	$91.91	8.800%	$99.9981	$100.00	$100.00	$100.00
Purchase #7	$112.80	9.342%	$123.3378	$123.34	$123.35	$123.30
7 purchase totals =	$736.86		$799.9859	$800.00	$800.00	$799.90