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	$203.84	4.364%	$212.7356	$212.74	$212.75	$212.70
Purchase #2	$99.80	9.540%	$109.3209	$109.32	$109.30	$109.30
Purchase #3	$174.69	4.559%	$182.6541	$182.65	$182.65	$182.70
Purchase #4	$171.60	11.273%	$190.9445	$190.94	$190.95	$190.90
Purchase #5	$156.82	9.616%	$171.8998	$171.90	$171.90	$171.90
Purchase #6	$52.41	7.730%	$56.4613	$56.46	$56.45	$56.50
Purchase #7	$74.72	12.813%	$84.2939	$84.29	$84.30	$84.30
7 purchase totals =	$933.88		$1,008.3101	$1,008.30	$1,008.30	$1,008.30