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	$84.46	10.278%	$93.1408	$93.14	$93.15	$93.10
Purchase #2	$38.81	13.199%	$43.9325	$43.93	$43.95	$43.90
Purchase #3	$177.94	10.391%	$196.4297	$196.43	$196.45	$196.40
Purchase #4	$172.32	6.191%	$182.9883	$182.99	$183.00	$183.00
Purchase #5	$175.80	3.411%	$181.7965	$181.80	$181.80	$181.80
Purchase #6	$39.50	4.579%	$41.3087	$41.31	$41.30	$41.30
Purchase #7	$233.62	13.105%	$264.2359	$264.24	$264.25	$264.20
7 purchase totals =	$922.45		$1,003.8324	$1,003.84	$1,003.90	$1,003.70