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	$167.90	7.714%	$180.8518	$180.85	$180.85	$180.90
Purchase #2	$168.66	12.715%	$190.1051	$190.11	$190.10	$190.10
Purchase #3	$77.76	6.868%	$83.1006	$83.10	$83.10	$83.10
Purchase #4	$207.43	3.364%	$214.4079	$214.41	$214.40	$214.40
Purchase #5	$151.62	8.380%	$164.3258	$164.33	$164.35	$164.30
Purchase #6	$101.96	11.514%	$113.6997	$113.70	$113.70	$113.70
Purchase #7	$199.27	11.264%	$221.7158	$221.72	$221.70	$221.70
7 purchase totals =	$1,074.60		$1,168.2067	$1,168.22	$1,168.20	$1,168.20