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	$151.57	9.283%	$165.6402	$165.64	$165.65	$165.60
Purchase #2	$249.89	9.284%	$273.0898	$273.09	$273.10	$273.10
Purchase #3	$225.51	11.498%	$251.4391	$251.44	$251.45	$251.40
Purchase #4	$85.36	5.166%	$89.7697	$89.77	$89.75	$89.80
Purchase #5	$216.90	12.789%	$244.6393	$244.64	$244.65	$244.60
Purchase #6	$57.92	9.607%	$63.4844	$63.48	$63.50	$63.50
Purchase #7	$128.66	12.615%	$144.8905	$144.89	$144.90	$144.90
7 purchase totals =	$1,115.81		$1,232.9530	$1,232.95	$1,233.00	$1,232.90