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	$248.67	11.562%	$277.4212	$277.42	$277.40	$277.40
Purchase #2	$212.56	5.768%	$224.8205	$224.82	$224.80	$224.80
Purchase #3	$136.61	11.547%	$152.3844	$152.38	$152.40	$152.40
Purchase #4	$12.30	12.854%	$13.881	$13.88	$13.90	$13.90
Purchase #5	$97.55	5.692%	$103.1025	$103.10	$103.10	$103.10
Purchase #6	$246.79	10.124%	$271.775	$271.78	$271.80	$271.80
Purchase #7	$77.79	9.871%	$85.4687	$85.47	$85.45	$85.50
7 purchase totals =	$1,032.27		$1,128.8533	$1,128.85	$1,128.85	$1,128.90