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	$184.45	5.497%	$194.5892	$194.59	$194.60	$194.60
Purchase #2	$102.41	11.606%	$114.2957	$114.30	$114.30	$114.30
Purchase #3	$135.36	11.325%	$150.6895	$150.69	$150.70	$150.70
Purchase #4	$66.54	9.159%	$72.6344	$72.63	$72.65	$72.60
Purchase #5	$125.82	13.429%	$142.7164	$142.72	$142.70	$142.70
Purchase #6	$60.70	9.489%	$66.4598	$66.46	$66.45	$66.50
Purchase #7	$84.75	7.623%	$91.2105	$91.21	$91.20	$91.20
7 purchase totals =	$760.03		$832.5955	$832.60	$832.60	$832.60