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	$10.56	9.789%	$11.5937	$11.59	$11.60	$11.60
Purchase #2	$215.29	7.423%	$231.271	$231.27	$231.25	$231.30
Purchase #3	$213.50	13.543%	$242.4143	$242.41	$242.40	$242.40
Purchase #4	$227.90	4.104%	$237.253	$237.25	$237.25	$237.30
Purchase #5	$55.49	10.134%	$61.1134	$61.11	$61.10	$61.10
Purchase #6	$57.46	8.868%	$62.5556	$62.56	$62.55	$62.60
Purchase #7	$225.96	10.424%	$249.5141	$249.51	$249.50	$249.50
7 purchase totals =	$1,006.16		$1,095.7151	$1,095.70	$1,095.65	$1,095.80