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	$80.60	5.781%	$85.2595	$85.26	$85.25	$85.30
Purchase #2	$186.58	5.262%	$196.3978	$196.40	$196.40	$196.40
Purchase #3	$193.26	3.151%	$199.3496	$199.35	$199.35	$199.30
Purchase #4	$90.94	8.192%	$98.3898	$98.39	$98.40	$98.40
Purchase #5	$145.64	10.463%	$160.8783	$160.88	$160.90	$160.90
Purchase #6	$250.41	5.188%	$263.4013	$263.40	$263.40	$263.40
Purchase #7	$33.81	9.534%	$37.0334	$37.03	$37.05	$37.00
7 purchase totals =	$981.24		$1,040.7097	$1,040.71	$1,040.75	$1,040.70