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	$124.63	4.360%	$130.0639	$130.06	$130.05	$130.10
Purchase #2	$234.99	8.847%	$255.7796	$255.78	$255.80	$255.80
Purchase #3	$41.54	12.160%	$46.5913	$46.59	$46.60	$46.60
Purchase #4	$30.65	9.359%	$33.5185	$33.52	$33.50	$33.50
Purchase #5	$208.61	5.609%	$220.3109	$220.31	$220.30	$220.30
Purchase #6	$148.80	5.366%	$156.7846	$156.78	$156.80	$156.80
Purchase #7	$72.57	13.471%	$82.3459	$82.35	$82.35	$82.30
7 purchase totals =	$861.79		$925.3947	$925.39	$925.40	$925.40