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	$38.64	7.505%	$41.5399	$41.54	$41.55	$41.50
Purchase #2	$91.35	8.298%	$98.9302	$98.93	$98.95	$98.90
Purchase #3	$182.85	7.331%	$196.2547	$196.25	$196.25	$196.30
Purchase #4	$154.96	6.727%	$165.3842	$165.38	$165.40	$165.40
Purchase #5	$47.89	9.734%	$52.5516	$52.55	$52.55	$52.60
Purchase #6	$75.78	10.588%	$83.8036	$83.80	$83.80	$83.80
Purchase #7	$246.31	12.405%	$276.8648	$276.86	$276.85	$276.90
7 purchase totals =	$837.78		$915.3290	$915.31	$915.35	$915.40