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	$61.58	12.236%	$69.1149	$69.11	$69.10	$69.10
Purchase #2	$153.69	13.791%	$174.8854	$174.89	$174.90	$174.90
Purchase #3	$102.73	10.741%	$113.7642	$113.76	$113.75	$113.80
Purchase #4	$96.33	4.522%	$100.686	$100.69	$100.70	$100.70
Purchase #5	$117.71	5.267%	$123.9098	$123.91	$123.90	$123.90
Purchase #6	$58.86	9.271%	$64.3169	$64.32	$64.30	$64.30
Purchase #7	$216.35	6.815%	$231.0943	$231.09	$231.10	$231.10
7 purchase totals =	$807.25		$877.7715	$877.77	$877.75	$877.80