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	$199.55	7.617%	$214.7497	$214.75	$214.75	$214.70
Purchase #2	$99.56	6.661%	$106.1917	$106.19	$106.20	$106.20
Purchase #3	$109.83	5.124%	$115.4577	$115.46	$115.45	$115.50
Purchase #4	$85.75	5.291%	$90.287	$90.29	$90.30	$90.30
Purchase #5	$41.66	12.576%	$46.8992	$46.90	$46.90	$46.90
Purchase #6	$218.37	6.843%	$233.3131	$233.31	$233.30	$233.30
Purchase #7	$11.55	7.612%	$12.4292	$12.43	$12.45	$12.40
7 purchase totals =	$766.27		$819.3276	$819.33	$819.35	$819.30