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	$208.51	5.460%	$219.8946	$219.89	$219.90	$219.90
Purchase #2	$245.31	11.819%	$274.3032	$274.30	$274.30	$274.30
Purchase #3	$121.83	10.196%	$134.2518	$134.25	$134.25	$134.30
Purchase #4	$181.46	3.853%	$188.4517	$188.45	$188.45	$188.50
Purchase #5	$50.55	3.396%	$52.2667	$52.27	$52.25	$52.30
Purchase #6	$198.26	7.841%	$213.8056	$213.81	$213.80	$213.80
Purchase #7	$11.67	6.756%	$12.4584	$12.46	$12.45	$12.50
7 purchase totals =	$1,017.59		$1,095.4320	$1,095.43	$1,095.40	$1,095.60