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	$154.30	10.597%	$170.6512	$170.65	$170.65	$170.70
Purchase #2	$47.78	6.444%	$50.8589	$50.86	$50.85	$50.90
Purchase #3	$205.44	8.197%	$222.2799	$222.28	$222.30	$222.30
Purchase #4	$133.32	3.678%	$138.2235	$138.22	$138.20	$138.20
Purchase #5	$250.80	8.108%	$271.1349	$271.13	$271.15	$271.10
Purchase #6	$75.45	9.812%	$82.8532	$82.85	$82.85	$82.90
Purchase #7	$110.29	12.112%	$123.6483	$123.65	$123.65	$123.60
7 purchase totals =	$977.38		$1,059.6499	$1,059.64	$1,059.65	$1,059.70