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	$187.85	5.426%	$198.0427	$198.04	$198.05	$198.00
Purchase #2	$226.41	13.808%	$257.6727	$257.67	$257.65	$257.70
Purchase #3	$36.93	3.767%	$38.3212	$38.32	$38.30	$38.30
Purchase #4	$220.43	7.604%	$237.1915	$237.19	$237.20	$237.20
Purchase #5	$184.58	3.715%	$191.4371	$191.44	$191.45	$191.40
Purchase #6	$72.36	8.362%	$78.4107	$78.41	$78.40	$78.40
Purchase #7	$88.82	11.387%	$98.9339	$98.93	$98.95	$98.90
7 purchase totals =	$1,017.38		$1,100.0098	$1,100.00	$1,100.00	$1,099.90