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	$246.58	7.637%	$265.4113	$265.41	$265.40	$265.40
Purchase #2	$38.59	6.404%	$41.0613	$41.06	$41.05	$41.10
Purchase #3	$94.92	3.155%	$97.9147	$97.91	$97.90	$97.90
Purchase #4	$158.86	12.319%	$178.43	$178.43	$178.45	$178.40
Purchase #5	$233.84	9.754%	$256.6488	$256.65	$256.65	$256.60
Purchase #6	$129.75	5.596%	$137.0108	$137.01	$137.00	$137.00
Purchase #7	$115.87	10.323%	$127.8313	$127.83	$127.85	$127.80
7 purchase totals =	$1,018.41		$1,104.3082	$1,104.30	$1,104.30	$1,104.20