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	$225.58	5.460%	$237.8967	$237.90	$237.90	$237.90
Purchase #2	$115.90	5.157%	$121.877	$121.88	$121.90	$121.90
Purchase #3	$73.57	11.128%	$81.7569	$81.76	$81.75	$81.80
Purchase #4	$223.49	6.452%	$237.9096	$237.91	$237.90	$237.90
Purchase #5	$172.57	13.845%	$196.4623	$196.46	$196.45	$196.50
Purchase #6	$130.90	6.850%	$139.8667	$139.87	$139.85	$139.90
Purchase #7	$42.48	6.642%	$45.3015	$45.30	$45.30	$45.30
7 purchase totals =	$984.49		$1,061.0707	$1,061.08	$1,061.05	$1,061.20