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	$132.47	9.678%	$145.2904	$145.29	$145.30	$145.30
Purchase #2	$188.77	12.494%	$212.3549	$212.35	$212.35	$212.40
Purchase #3	$172.42	5.488%	$181.8824	$181.88	$181.90	$181.90
Purchase #4	$46.76	13.698%	$53.1652	$53.17	$53.15	$53.20
Purchase #5	$27.85	13.217%	$31.5309	$31.53	$31.55	$31.50
Purchase #6	$204.91	9.322%	$224.0117	$224.01	$224.00	$224.00
Purchase #7	$193.31	13.616%	$219.6311	$219.63	$219.65	$219.60
7 purchase totals =	$966.49		$1,067.8666	$1,067.86	$1,067.90	$1,067.90