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	$108.47	5.539%	$114.4782	$114.48	$114.50	$114.50
Purchase #2	$123.33	6.254%	$131.0431	$131.04	$131.05	$131.00
Purchase #3	$178.46	6.373%	$189.8333	$189.83	$189.85	$189.80
Purchase #4	$215.31	8.467%	$233.5403	$233.54	$233.55	$233.50
Purchase #5	$225.56	13.314%	$255.5911	$255.59	$255.60	$255.60
Purchase #6	$68.93	7.595%	$74.1652	$74.17	$74.15	$74.20
Purchase #7	$62.73	13.672%	$71.3064	$71.31	$71.30	$71.30
7 purchase totals =	$982.79		$1,069.9576	$1,069.96	$1,070.00	$1,069.90