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	$84.26	7.698%	$90.7463	$90.75	$90.75	$90.70
Purchase #2	$65.73	9.317%	$71.8541	$71.85	$71.85	$71.90
Purchase #3	$71.98	12.161%	$80.7335	$80.73	$80.75	$80.70
Purchase #4	$131.88	7.713%	$142.0519	$142.05	$142.05	$142.10
Purchase #5	$98.72	3.635%	$102.3085	$102.31	$102.30	$102.30
Purchase #6	$75.47	4.375%	$78.7718	$78.77	$78.75	$78.80
Purchase #7	$208.81	3.416%	$215.9429	$215.94	$215.95	$215.90
7 purchase totals =	$736.85		$782.4090	$782.40	$782.40	$782.40