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	$236.89	7.717%	$255.1708	$255.17	$255.15	$255.20
Purchase #2	$85.46	9.435%	$93.5232	$93.52	$93.50	$93.50
Purchase #3	$225.65	4.643%	$236.1269	$236.13	$236.15	$236.10
Purchase #4	$82.28	4.758%	$86.1949	$86.19	$86.20	$86.20
Purchase #5	$31.48	4.131%	$32.7804	$32.78	$32.80	$32.80
Purchase #6	$208.39	12.801%	$235.066	$235.07	$235.05	$235.10
Purchase #7	$66.36	9.156%	$72.4359	$72.44	$72.45	$72.40
7 purchase totals =	$936.51		$1,011.2981	$1,011.30	$1,011.30	$1,011.30