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	$164.27	6.808%	$175.4535	$175.45	$175.45	$175.50
Purchase #2	$78.63	9.309%	$85.9497	$85.95	$85.95	$85.90
Purchase #3	$143.98	13.126%	$162.8788	$162.88	$162.90	$162.90
Purchase #4	$131.61	6.709%	$140.4397	$140.44	$140.45	$140.40
Purchase #5	$147.54	11.666%	$164.752	$164.75	$164.75	$164.80
Purchase #6	$175.36	10.110%	$193.0889	$193.09	$193.10	$193.10
Purchase #7	$196.86	12.150%	$220.7785	$220.78	$220.80	$220.80
7 purchase totals =	$1,038.25		$1,143.3411	$1,143.34	$1,143.40	$1,143.40