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	$180.97	13.768%	$205.8859	$205.89	$205.90	$205.90
Purchase #2	$53.81	10.369%	$59.3896	$59.39	$59.40	$59.40
Purchase #3	$197.85	10.710%	$219.0397	$219.04	$219.05	$219.00
Purchase #4	$99.98	8.104%	$108.0824	$108.08	$108.10	$108.10
Purchase #5	$36.79	9.757%	$40.3796	$40.38	$40.40	$40.40
Purchase #6	$133.25	13.118%	$150.7297	$150.73	$150.75	$150.70
Purchase #7	$229.54	5.757%	$242.7546	$242.75	$242.75	$242.80
7 purchase totals =	$932.19		$1,026.2615	$1,026.26	$1,026.35	$1,026.30