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	$112.81	13.432%	$127.9626	$127.96	$127.95	$128.00
Purchase #2	$78.87	10.187%	$86.9045	$86.90	$86.90	$86.90
Purchase #3	$38.30	9.814%	$42.0588	$42.06	$42.05	$42.10
Purchase #4	$242.67	7.694%	$261.341	$261.34	$261.35	$261.30
Purchase #5	$185.64	5.767%	$196.3459	$196.35	$196.35	$196.30
Purchase #6	$168.57	3.704%	$174.8138	$174.81	$174.80	$174.80
Purchase #7	$147.69	9.396%	$161.567	$161.57	$161.55	$161.60
7 purchase totals =	$974.55		$1,050.9936	$1,050.99	$1,050.95	$1,051.00