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	$180.83	9.830%	$198.6056	$198.61	$198.60	$198.60
Purchase #2	$61.28	4.401%	$63.9769	$63.98	$64.00	$64.00
Purchase #3	$65.90	13.417%	$74.7418	$74.74	$74.75	$74.70
Purchase #4	$29.48	6.538%	$31.4074	$31.41	$31.40	$31.40
Purchase #5	$172.96	6.849%	$184.806	$184.81	$184.80	$184.80
Purchase #6	$207.27	6.839%	$221.4452	$221.45	$221.45	$221.40
Purchase #7	$157.48	9.789%	$172.8957	$172.90	$172.90	$172.90
7 purchase totals =	$875.20		$947.8786	$947.90	$947.90	$947.80