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	$132.53	12.412%	$148.9796	$148.98	$149.00	$149.00
Purchase #2	$180.88	7.857%	$195.0917	$195.09	$195.10	$195.10
Purchase #3	$84.98	13.569%	$96.5109	$96.51	$96.50	$96.50
Purchase #4	$53.39	10.821%	$59.1673	$59.17	$59.15	$59.20
Purchase #5	$156.62	7.670%	$168.6328	$168.63	$168.65	$168.60
Purchase #6	$105.67	6.523%	$112.5629	$112.56	$112.55	$112.60
Purchase #7	$145.59	3.624%	$150.8662	$150.87	$150.85	$150.90
7 purchase totals =	$859.66		$931.8114	$931.81	$931.80	$931.90