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	$229.87	10.706%	$254.4799	$254.48	$254.50	$254.50
Purchase #2	$41.87	9.485%	$45.8414	$45.84	$45.85	$45.80
Purchase #3	$32.87	12.563%	$36.9995	$37.00	$37.00	$37.00
Purchase #4	$92.79	10.520%	$102.5515	$102.55	$102.55	$102.60
Purchase #5	$224.57	4.368%	$234.3792	$234.38	$234.40	$234.40
Purchase #6	$141.81	4.675%	$148.4396	$148.44	$148.45	$148.40
Purchase #7	$232.60	13.812%	$264.7267	$264.73	$264.75	$264.70
7 purchase totals =	$996.38		$1,087.4178	$1,087.42	$1,087.50	$1,087.40