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	$101.54	3.846%	$105.4452	$105.45	$105.45	$105.40
Purchase #2	$245.77	9.676%	$269.5507	$269.55	$269.55	$269.60
Purchase #3	$64.63	12.803%	$72.9046	$72.90	$72.90	$72.90
Purchase #4	$181.50	8.209%	$196.3993	$196.40	$196.40	$196.40
Purchase #5	$175.77	10.146%	$193.6036	$193.60	$193.60	$193.60
Purchase #6	$51.68	7.699%	$55.6588	$55.66	$55.65	$55.70
Purchase #7	$28.45	4.749%	$29.8011	$29.80	$29.80	$29.80
7 purchase totals =	$849.34		$923.3633	$923.36	$923.35	$923.40