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	$104.95	9.833%	$115.2697	$115.27	$115.25	$115.30
Purchase #2	$173.91	12.792%	$196.1566	$196.16	$196.15	$196.20
Purchase #3	$136.95	8.439%	$148.5072	$148.51	$148.50	$148.50
Purchase #4	$154.39	13.268%	$174.8745	$174.87	$174.85	$174.90
Purchase #5	$174.61	8.257%	$189.0275	$189.03	$189.05	$189.00
Purchase #6	$101.34	3.148%	$104.5302	$104.53	$104.55	$104.50
Purchase #7	$128.68	6.728%	$137.3376	$137.34	$137.35	$137.30
7 purchase totals =	$974.83		$1,065.7033	$1,065.71	$1,065.70	$1,065.70