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	$41.62	4.388%	$43.4463	$43.45	$43.45	$43.40
Purchase #2	$120.70	7.574%	$129.8418	$129.84	$129.85	$129.80
Purchase #3	$205.78	6.554%	$219.2668	$219.27	$219.25	$219.30
Purchase #4	$205.98	8.106%	$222.6767	$222.68	$222.70	$222.70
Purchase #5	$7.61	3.326%	$7.8631	$7.86	$7.85	$7.90
Purchase #6	$141.79	8.839%	$154.3228	$154.32	$154.30	$154.30
Purchase #7	$211.84	5.654%	$223.8174	$223.82	$223.80	$223.80
7 purchase totals =	$935.32		$1,001.2349	$1,001.24	$1,001.20	$1,001.20