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	$88.32	5.375%	$93.0672	$93.07	$93.05	$93.10
Purchase #2	$111.98	6.866%	$119.6685	$119.67	$119.65	$119.70
Purchase #3	$78.71	13.758%	$89.5389	$89.54	$89.55	$89.50
Purchase #4	$131.87	8.107%	$142.5607	$142.56	$142.55	$142.60
Purchase #5	$208.98	8.289%	$226.3024	$226.30	$226.30	$226.30
Purchase #6	$112.93	9.340%	$123.4777	$123.48	$123.50	$123.50
Purchase #7	$180.47	3.620%	$187.003	$187.00	$187.00	$187.00
7 purchase totals =	$913.26		$981.6184	$981.62	$981.60	$981.70