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	$185.49	10.727%	$205.3875	$205.39	$205.40	$205.40
Purchase #2	$228.91	4.720%	$239.7146	$239.71	$239.70	$239.70
Purchase #3	$93.89	3.768%	$97.4278	$97.43	$97.45	$97.40
Purchase #4	$131.34	7.498%	$141.1879	$141.19	$141.20	$141.20
Purchase #5	$167.36	12.866%	$188.8925	$188.89	$188.90	$188.90
Purchase #6	$136.33	10.677%	$150.886	$150.89	$150.90	$150.90
Purchase #7	$35.48	8.585%	$38.526	$38.53	$38.55	$38.50
7 purchase totals =	$978.80		$1,062.0223	$1,062.03	$1,062.10	$1,062.00