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	$32.94	7.481%	$35.4042	$35.40	$35.40	$35.40
Purchase #2	$104.99	13.686%	$119.3589	$119.36	$119.35	$119.40
Purchase #3	$78.97	12.793%	$89.0726	$89.07	$89.05	$89.10
Purchase #4	$178.77	6.837%	$190.9925	$190.99	$191.00	$191.00
Purchase #5	$57.64	12.481%	$64.834	$64.83	$64.85	$64.80
Purchase #6	$59.31	4.417%	$61.9297	$61.93	$61.95	$61.90
Purchase #7	$52.48	11.661%	$58.5997	$58.60	$58.60	$58.60
7 purchase totals =	$565.10		$620.1916	$620.18	$620.20	$620.20