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	$202.98	13.775%	$230.9405	$230.94	$230.95	$230.90
Purchase #2	$198.29	6.542%	$211.2621	$211.26	$211.25	$211.30
Purchase #3	$97.93	12.232%	$109.9088	$109.91	$109.90	$109.90
Purchase #4	$110.58	8.483%	$119.9605	$119.96	$119.95	$120.00
Purchase #5	$37.80	13.545%	$42.92	$42.92	$42.90	$42.90
Purchase #6	$186.54	5.549%	$196.8911	$196.89	$196.90	$196.90
Purchase #7	$130.74	7.543%	$140.6017	$140.60	$140.60	$140.60
7 purchase totals =	$964.86		$1,052.4847	$1,052.48	$1,052.45	$1,052.50