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	$181.88	5.543%	$191.9616	$191.96	$191.95	$192.00
Purchase #2	$80.84	7.511%	$86.9119	$86.91	$86.90	$86.90
Purchase #3	$66.30	4.681%	$69.4035	$69.40	$69.40	$69.40
Purchase #4	$157.86	13.781%	$179.6147	$179.61	$179.60	$179.60
Purchase #5	$113.70	11.837%	$127.1587	$127.16	$127.15	$127.20
Purchase #6	$44.78	12.212%	$50.2485	$50.25	$50.25	$50.20
Purchase #7	$209.35	9.202%	$228.6144	$228.61	$228.60	$228.60
7 purchase totals =	$854.71		$933.9133	$933.90	$933.85	$933.90