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	$179.72	7.284%	$192.8108	$192.81	$192.80	$192.80
Purchase #2	$80.46	6.373%	$85.5877	$85.59	$85.60	$85.60
Purchase #3	$235.60	6.486%	$250.881	$250.88	$250.90	$250.90
Purchase #4	$51.49	3.536%	$53.3107	$53.31	$53.30	$53.30
Purchase #5	$154.93	11.563%	$172.8446	$172.84	$172.85	$172.80
Purchase #6	$40.57	5.795%	$42.921	$42.92	$42.90	$42.90
Purchase #7	$137.82	9.242%	$150.5573	$150.56	$150.55	$150.60
7 purchase totals =	$880.59		$948.9131	$948.91	$948.90	$948.90