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	$141.25	9.166%	$154.197	$154.20	$154.20	$154.20
Purchase #2	$96.34	7.580%	$103.6426	$103.64	$103.65	$103.60
Purchase #3	$176.72	11.155%	$196.4331	$196.43	$196.45	$196.40
Purchase #4	$82.99	3.453%	$85.8556	$85.86	$85.85	$85.90
Purchase #5	$55.84	12.612%	$62.8825	$62.88	$62.90	$62.90
Purchase #6	$239.51	12.459%	$269.3506	$269.35	$269.35	$269.40
Purchase #7	$115.88	10.244%	$127.7507	$127.75	$127.75	$127.80
7 purchase totals =	$908.53		$1,000.1121	$1,000.11	$1,000.15	$1,000.20