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	$190.29	3.493%	$196.9368	$196.94	$196.95	$196.90
Purchase #2	$245.73	10.331%	$271.1164	$271.12	$271.10	$271.10
Purchase #3	$231.79	13.748%	$263.6565	$263.66	$263.65	$263.70
Purchase #4	$128.50	10.326%	$141.7689	$141.77	$141.75	$141.80
Purchase #5	$104.72	11.762%	$117.0372	$117.04	$117.05	$117.00
Purchase #6	$58.88	6.226%	$62.5459	$62.55	$62.55	$62.50
Purchase #7	$163.75	6.436%	$174.289	$174.29	$174.30	$174.30
7 purchase totals =	$1,123.66		$1,227.3507	$1,227.37	$1,227.35	$1,227.30