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	$168.74	8.271%	$182.6965	$182.70	$182.70	$182.70
Purchase #2	$140.29	3.684%	$145.4583	$145.46	$145.45	$145.50
Purchase #3	$72.67	5.763%	$76.858	$76.86	$76.85	$76.90
Purchase #4	$198.71	5.461%	$209.5616	$209.56	$209.55	$209.60
Purchase #5	$51.72	11.860%	$57.854	$57.85	$57.85	$57.90
Purchase #6	$48.31	13.799%	$54.9763	$54.98	$55.00	$55.00
Purchase #7	$139.36	9.293%	$152.3107	$152.31	$152.30	$152.30
7 purchase totals =	$819.80		$879.7154	$879.72	$879.70	$879.90