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	$214.76	13.443%	$243.6302	$243.63	$243.65	$243.60
Purchase #2	$227.90	12.137%	$255.5602	$255.56	$255.55	$255.60
Purchase #3	$27.66	7.717%	$29.7945	$29.79	$29.80	$29.80
Purchase #4	$69.32	13.607%	$78.7524	$78.75	$78.75	$78.80
Purchase #5	$120.76	9.571%	$132.3179	$132.32	$132.30	$132.30
Purchase #6	$68.70	6.836%	$73.3963	$73.40	$73.40	$73.40
Purchase #7	$110.42	4.870%	$115.7975	$115.80	$115.80	$115.80
7 purchase totals =	$839.52		$929.2490	$929.25	$929.25	$929.30