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	$180.78	9.560%	$198.0626	$198.06	$198.05	$198.10
Purchase #2	$114.72	7.675%	$123.5248	$123.52	$123.50	$123.50
Purchase #3	$110.96	8.111%	$119.96	$119.96	$119.95	$120.00
Purchase #4	$37.56	8.728%	$40.8382	$40.84	$40.85	$40.80
Purchase #5	$243.53	11.121%	$270.613	$270.61	$270.60	$270.60
Purchase #6	$183.58	11.509%	$204.7082	$204.71	$204.70	$204.70
Purchase #7	$138.95	8.539%	$150.8149	$150.81	$150.80	$150.80
7 purchase totals =	$1,010.08		$1,108.5217	$1,108.51	$1,108.45	$1,108.50