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	$218.83	11.419%	$243.8182	$243.82	$243.80	$243.80
Purchase #2	$24.63	12.558%	$27.723	$27.72	$27.70	$27.70
Purchase #3	$41.73	6.742%	$44.5434	$44.54	$44.55	$44.50
Purchase #4	$135.57	5.136%	$142.5329	$142.53	$142.55	$142.50
Purchase #5	$152.56	3.716%	$158.2291	$158.23	$158.25	$158.20
Purchase #6	$85.58	5.715%	$90.4709	$90.47	$90.45	$90.50
Purchase #7	$92.80	9.125%	$101.268	$101.27	$101.25	$101.30
7 purchase totals =	$751.70		$808.5855	$808.58	$808.55	$808.50