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	$120.85	5.831%	$127.8968	$127.90	$127.90	$127.90
Purchase #2	$64.99	9.388%	$71.0913	$71.09	$71.10	$71.10
Purchase #3	$45.33	13.334%	$51.3743	$51.37	$51.35	$51.40
Purchase #4	$140.48	6.804%	$150.0383	$150.04	$150.05	$150.00
Purchase #5	$43.99	12.737%	$49.593	$49.59	$49.60	$49.60
Purchase #6	$150.81	3.636%	$156.2935	$156.29	$156.30	$156.30
Purchase #7	$184.74	3.277%	$190.7939	$190.79	$190.80	$190.80
7 purchase totals =	$751.19		$797.0811	$797.07	$797.10	$797.10