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	$145.34	5.720%	$153.6534	$153.65	$153.65	$153.70
Purchase #2	$182.33	4.499%	$190.533	$190.53	$190.55	$190.50
Purchase #3	$13.72	4.354%	$14.3174	$14.32	$14.30	$14.30
Purchase #4	$160.83	4.230%	$167.6331	$167.63	$167.65	$167.60
Purchase #5	$216.43	10.364%	$238.8608	$238.86	$238.85	$238.90
Purchase #6	$27.37	3.551%	$28.3419	$28.34	$28.35	$28.30
Purchase #7	$112.78	10.438%	$124.552	$124.55	$124.55	$124.60
7 purchase totals =	$858.80		$917.8916	$917.88	$917.90	$917.90