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	$93.60	11.627%	$104.4829	$104.48	$104.50	$104.50
Purchase #2	$93.91	12.206%	$105.3727	$105.37	$105.35	$105.40
Purchase #3	$213.88	9.716%	$234.6606	$234.66	$234.65	$234.70
Purchase #4	$169.51	13.824%	$192.9431	$192.94	$192.95	$192.90
Purchase #5	$218.77	13.497%	$248.2974	$248.30	$248.30	$248.30
Purchase #6	$120.61	8.658%	$131.0524	$131.05	$131.05	$131.10
Purchase #7	$126.37	12.354%	$141.9817	$141.98	$142.00	$142.00
7 purchase totals =	$1,036.65		$1,158.7908	$1,158.78	$1,158.80	$1,158.90