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	$130.46	10.539%	$144.2092	$144.21	$144.20	$144.20
Purchase #2	$39.45	10.367%	$43.5398	$43.54	$43.55	$43.50
Purchase #3	$6.59	3.474%	$6.8189	$6.82	$6.80	$6.80
Purchase #4	$195.46	4.558%	$204.3691	$204.37	$204.35	$204.40
Purchase #5	$32.66	5.404%	$34.4249	$34.42	$34.40	$34.40
Purchase #6	$193.91	7.739%	$208.9167	$208.92	$208.90	$208.90
Purchase #7	$167.25	10.695%	$185.1374	$185.14	$185.15	$185.10
7 purchase totals =	$765.78		$827.4160	$827.42	$827.35	$827.30