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	$222.60	5.637%	$235.148	$235.15	$235.15	$235.10
Purchase #2	$6.85	10.751%	$7.5864	$7.59	$7.60	$7.60
Purchase #3	$76.55	13.387%	$86.7977	$86.80	$86.80	$86.80
Purchase #4	$213.38	7.855%	$230.141	$230.14	$230.15	$230.10
Purchase #5	$242.66	7.122%	$259.9422	$259.94	$259.95	$259.90
Purchase #6	$86.39	3.715%	$89.5994	$89.60	$89.60	$89.60
Purchase #7	$34.80	3.552%	$36.0361	$36.04	$36.05	$36.00
7 purchase totals =	$883.23		$945.2508	$945.26	$945.30	$945.10