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	$59.77	6.551%	$63.6855	$63.69	$63.70	$63.70
Purchase #2	$12.46	5.324%	$13.1234	$13.12	$13.10	$13.10
Purchase #3	$7.42	6.597%	$7.9095	$7.91	$7.90	$7.90
Purchase #4	$116.25	6.242%	$123.5063	$123.51	$123.50	$123.50
Purchase #5	$133.72	13.498%	$151.7695	$151.77	$151.75	$151.80
Purchase #6	$174.84	7.529%	$188.0037	$188.00	$188.00	$188.00
Purchase #7	$114.25	4.195%	$119.0428	$119.04	$119.05	$119.00
7 purchase totals =	$618.71		$667.0407	$667.04	$667.00	$667.00