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	$96.59	13.826%	$109.9445	$109.94	$109.95	$109.90
Purchase #2	$207.97	7.113%	$222.7629	$222.76	$222.75	$222.80
Purchase #3	$9.68	4.110%	$10.0778	$10.08	$10.10	$10.10
Purchase #4	$196.72	12.789%	$221.8785	$221.88	$221.90	$221.90
Purchase #5	$238.62	11.287%	$265.553	$265.55	$265.55	$265.60
Purchase #6	$71.96	9.562%	$78.8408	$78.84	$78.85	$78.80
Purchase #7	$167.59	5.741%	$177.2113	$177.21	$177.20	$177.20
7 purchase totals =	$989.13		$1,086.2688	$1,086.26	$1,086.30	$1,086.30