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	$140.82	11.305%	$156.7397	$156.74	$156.75	$156.70
Purchase #2	$135.32	13.126%	$153.0821	$153.08	$153.10	$153.10
Purchase #3	$250.61	12.837%	$282.7808	$282.78	$282.80	$282.80
Purchase #4	$181.37	6.613%	$193.364	$193.36	$193.35	$193.40
Purchase #5	$28.55	9.403%	$31.2346	$31.23	$31.25	$31.20
Purchase #6	$85.85	9.380%	$93.9027	$93.90	$93.90	$93.90
Purchase #7	$180.40	11.262%	$200.7166	$200.72	$200.70	$200.70
7 purchase totals =	$1,002.92		$1,111.8205	$1,111.81	$1,111.85	$1,111.80