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	$129.48	12.197%	$145.2727	$145.27	$145.25	$145.30
Purchase #2	$82.45	13.299%	$93.415	$93.42	$93.40	$93.40
Purchase #3	$54.87	7.719%	$59.1054	$59.11	$59.10	$59.10
Purchase #4	$175.77	4.732%	$184.0874	$184.09	$184.10	$184.10
Purchase #5	$245.53	13.819%	$279.4598	$279.46	$279.45	$279.50
Purchase #6	$188.83	12.375%	$212.1977	$212.20	$212.20	$212.20
Purchase #7	$41.83	3.831%	$43.4325	$43.43	$43.45	$43.40
7 purchase totals =	$918.76		$1,016.9705	$1,016.98	$1,016.95	$1,017.00