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	$105.33	9.826%	$115.6797	$115.68	$115.70	$115.70
Purchase #2	$242.42	3.317%	$250.4611	$250.46	$250.45	$250.50
Purchase #3	$39.27	6.670%	$41.8893	$41.89	$41.90	$41.90
Purchase #4	$150.52	5.546%	$158.8678	$158.87	$158.85	$158.90
Purchase #5	$146.38	11.181%	$162.7467	$162.75	$162.75	$162.70
Purchase #6	$171.37	4.865%	$179.7072	$179.71	$179.70	$179.70
Purchase #7	$39.80	4.331%	$41.5237	$41.52	$41.50	$41.50
7 purchase totals =	$895.09		$950.8755	$950.88	$950.85	$950.90