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	$128.90	4.689%	$134.9441	$134.94	$134.95	$134.90
Purchase #2	$191.41	13.216%	$216.7067	$216.71	$216.70	$216.70
Purchase #3	$222.37	9.496%	$243.4863	$243.49	$243.50	$243.50
Purchase #4	$94.66	11.750%	$105.7826	$105.78	$105.80	$105.80
Purchase #5	$159.26	5.757%	$168.4286	$168.43	$168.45	$168.40
Purchase #6	$102.27	10.155%	$112.6555	$112.66	$112.65	$112.70
Purchase #7	$40.31	13.204%	$45.6325	$45.63	$45.65	$45.60
7 purchase totals =	$939.18		$1,027.6363	$1,027.64	$1,027.70	$1,027.60