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	$42.49	12.792%	$47.9253	$47.93	$47.95	$47.90
Purchase #2	$158.85	13.664%	$180.5553	$180.56	$180.55	$180.60
Purchase #3	$79.39	10.300%	$87.5672	$87.57	$87.55	$87.60
Purchase #4	$55.89	10.192%	$61.5863	$61.59	$61.60	$61.60
Purchase #5	$115.72	11.296%	$128.7917	$128.79	$128.80	$128.80
Purchase #6	$155.73	10.297%	$171.7655	$171.77	$171.75	$171.80
Purchase #7	$177.64	5.845%	$188.0231	$188.02	$188.00	$188.00
7 purchase totals =	$785.71		$866.2144	$866.23	$866.20	$866.30