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	$113.70	4.605%	$118.9359	$118.94	$118.95	$118.90
Purchase #2	$77.80	13.857%	$88.5807	$88.58	$88.60	$88.60
Purchase #3	$128.44	9.443%	$140.5686	$140.57	$140.55	$140.60
Purchase #4	$166.96	3.217%	$172.3311	$172.33	$172.35	$172.30
Purchase #5	$40.78	10.794%	$45.1818	$45.18	$45.20	$45.20
Purchase #6	$188.30	4.540%	$196.8488	$196.85	$196.85	$196.80
Purchase #7	$81.76	10.872%	$90.6489	$90.65	$90.65	$90.60
7 purchase totals =	$797.74		$853.0958	$853.10	$853.15	$853.00