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	$203.42	12.486%	$228.819	$228.82	$228.80	$228.80
Purchase #2	$13.53	13.231%	$15.3202	$15.32	$15.30	$15.30
Purchase #3	$168.69	12.116%	$189.1285	$189.13	$189.15	$189.10
Purchase #4	$58.49	5.706%	$61.8274	$61.83	$61.85	$61.80
Purchase #5	$194.71	10.411%	$214.9813	$214.98	$215.00	$215.00
Purchase #6	$178.85	6.855%	$191.1102	$191.11	$191.10	$191.10
Purchase #7	$176.42	13.164%	$199.6439	$199.64	$199.65	$199.60
7 purchase totals =	$994.11		$1,100.8305	$1,100.83	$1,100.85	$1,100.70