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	$38.69	8.380%	$41.9322	$41.93	$41.95	$41.90
Purchase #2	$55.90	13.268%	$63.3168	$63.32	$63.30	$63.30
Purchase #3	$214.86	8.713%	$233.5808	$233.58	$233.60	$233.60
Purchase #4	$85.27	10.794%	$94.474	$94.47	$94.45	$94.50
Purchase #5	$110.67	11.399%	$123.2853	$123.29	$123.30	$123.30
Purchase #6	$103.31	6.552%	$110.0789	$110.08	$110.10	$110.10
Purchase #7	$245.33	11.652%	$273.9159	$273.92	$273.90	$273.90
7 purchase totals =	$854.03		$940.5839	$940.59	$940.60	$940.60