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	$240.34	13.411%	$272.572	$272.57	$272.55	$272.60
Purchase #2	$76.92	11.331%	$85.6358	$85.64	$85.65	$85.60
Purchase #3	$156.77	6.783%	$167.4037	$167.40	$167.40	$167.40
Purchase #4	$159.25	4.575%	$166.5357	$166.54	$166.55	$166.50
Purchase #5	$201.59	3.496%	$208.6376	$208.64	$208.65	$208.60
Purchase #6	$43.67	10.626%	$48.3104	$48.31	$48.30	$48.30
Purchase #7	$36.37	3.183%	$37.5277	$37.53	$37.55	$37.50
7 purchase totals =	$914.91		$986.6229	$986.63	$986.65	$986.50