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	$230.50	4.744%	$241.4349	$241.43	$241.45	$241.40
Purchase #2	$99.40	10.639%	$109.9752	$109.98	$110.00	$110.00
Purchase #3	$176.34	12.641%	$198.6311	$198.63	$198.65	$198.60
Purchase #4	$194.29	12.592%	$218.755	$218.76	$218.75	$218.80
Purchase #5	$164.72	8.253%	$178.3143	$178.31	$178.30	$178.30
Purchase #6	$66.77	7.159%	$71.5501	$71.55	$71.55	$71.60
Purchase #7	$155.32	11.517%	$173.2082	$173.21	$173.20	$173.20
7 purchase totals =	$1,087.34		$1,191.8688	$1,191.87	$1,191.90	$1,191.90