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	$218.73	9.222%	$238.9013	$238.90	$238.90	$238.90
Purchase #2	$109.82	4.356%	$114.6038	$114.60	$114.60	$114.60
Purchase #3	$98.47	5.317%	$103.7056	$103.71	$103.70	$103.70
Purchase #4	$162.89	6.515%	$173.5023	$173.50	$173.50	$173.50
Purchase #5	$62.48	10.716%	$69.1754	$69.18	$69.20	$69.20
Purchase #6	$188.47	7.411%	$202.4375	$202.44	$202.45	$202.40
Purchase #7	$176.86	12.839%	$199.5671	$199.57	$199.55	$199.60
7 purchase totals =	$1,017.72		$1,101.8930	$1,101.90	$1,101.90	$1,101.90