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	$30.39	10.219%	$33.4956	$33.50	$33.50	$33.50
Purchase #2	$55.37	11.277%	$61.6141	$61.61	$61.60	$61.60
Purchase #3	$82.93	11.159%	$92.1842	$92.18	$92.20	$92.20
Purchase #4	$248.67	6.524%	$264.8932	$264.89	$264.90	$264.90
Purchase #5	$159.95	13.531%	$181.5928	$181.59	$181.60	$181.60
Purchase #6	$188.47	10.659%	$208.559	$208.56	$208.55	$208.60
Purchase #7	$83.33	11.257%	$92.7105	$92.71	$92.70	$92.70
7 purchase totals =	$849.11		$935.0494	$935.04	$935.05	$935.10