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	$123.60	3.460%	$127.8766	$127.88	$127.90	$127.90
Purchase #2	$181.29	3.658%	$187.9216	$187.92	$187.90	$187.90
Purchase #3	$141.90	6.844%	$151.6116	$151.61	$151.60	$151.60
Purchase #4	$167.71	10.209%	$184.8315	$184.83	$184.85	$184.80
Purchase #5	$61.54	3.684%	$63.8071	$63.81	$63.80	$63.80
Purchase #6	$192.82	3.714%	$199.9813	$199.98	$200.00	$200.00
Purchase #7	$194.27	10.427%	$214.5265	$214.53	$214.55	$214.50
7 purchase totals =	$1,063.13		$1,130.5562	$1,130.56	$1,130.60	$1,130.50