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	$68.41	5.710%	$72.3162	$72.32	$72.30	$72.30
Purchase #2	$111.50	11.749%	$124.6001	$124.60	$124.60	$124.60
Purchase #3	$201.87	11.285%	$224.651	$224.65	$224.65	$224.70
Purchase #4	$249.89	12.364%	$280.7864	$280.79	$280.80	$280.80
Purchase #5	$99.92	9.748%	$109.6602	$109.66	$109.65	$109.70
Purchase #6	$166.64	3.179%	$171.9375	$171.94	$171.95	$171.90
Purchase #7	$198.77	11.803%	$222.2308	$222.23	$222.25	$222.20
7 purchase totals =	$1,097.00		$1,206.1822	$1,206.19	$1,206.20	$1,206.20