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	$102.59	11.163%	$114.0421	$114.04	$114.05	$114.00
Purchase #2	$115.74	13.223%	$131.0443	$131.04	$131.05	$131.00
Purchase #3	$208.59	8.284%	$225.8696	$225.87	$225.85	$225.90
Purchase #4	$228.63	11.206%	$254.2503	$254.25	$254.25	$254.30
Purchase #5	$174.48	6.522%	$185.8596	$185.86	$185.85	$185.90
Purchase #6	$35.49	7.655%	$38.2068	$38.21	$38.20	$38.20
Purchase #7	$125.71	4.252%	$131.0552	$131.06	$131.05	$131.10
7 purchase totals =	$991.23		$1,080.3279	$1,080.33	$1,080.30	$1,080.40