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	$82.39	4.630%	$86.2047	$86.20	$86.20	$86.20
Purchase #2	$175.34	3.445%	$181.3805	$181.38	$181.40	$181.40
Purchase #3	$56.76	4.261%	$59.1785	$59.18	$59.20	$59.20
Purchase #4	$58.42	7.466%	$62.7816	$62.78	$62.80	$62.80
Purchase #5	$49.76	3.285%	$51.3946	$51.39	$51.40	$51.40
Purchase #6	$147.73	12.455%	$166.1298	$166.13	$166.15	$166.10
Purchase #7	$183.41	11.640%	$204.7589	$204.76	$204.75	$204.80
7 purchase totals =	$753.81		$811.8286	$811.82	$811.90	$811.90