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	$88.87	10.699%	$98.3782	$98.38	$98.40	$98.40
Purchase #2	$240.39	9.134%	$262.3472	$262.35	$262.35	$262.30
Purchase #3	$211.88	9.302%	$231.5891	$231.59	$231.60	$231.60
Purchase #4	$82.75	3.447%	$85.6024	$85.60	$85.60	$85.60
Purchase #5	$49.37	9.157%	$53.8908	$53.89	$53.90	$53.90
Purchase #6	$173.67	10.297%	$191.5528	$191.55	$191.55	$191.60
Purchase #7	$157.76	7.292%	$169.2639	$169.26	$169.25	$169.30
7 purchase totals =	$1,004.69		$1,092.6244	$1,092.62	$1,092.65	$1,092.70