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	$181.77	9.366%	$198.7946	$198.79	$198.80	$198.80
Purchase #2	$40.39	13.498%	$45.8418	$45.84	$45.85	$45.80
Purchase #3	$156.73	4.832%	$164.3032	$164.30	$164.30	$164.30
Purchase #4	$203.40	10.371%	$224.4946	$224.49	$224.50	$224.50
Purchase #5	$213.67	12.589%	$240.5689	$240.57	$240.55	$240.60
Purchase #6	$35.60	10.809%	$39.448	$39.45	$39.45	$39.40
Purchase #7	$223.33	6.640%	$238.1591	$238.16	$238.15	$238.20
7 purchase totals =	$1,054.89		$1,151.6102	$1,151.60	$1,151.60	$1,151.60