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	$232.50	4.290%	$242.4743	$242.47	$242.45	$242.50
Purchase #2	$248.34	9.502%	$271.9373	$271.94	$271.95	$271.90
Purchase #3	$49.69	5.595%	$52.4702	$52.47	$52.45	$52.50
Purchase #4	$46.90	9.497%	$51.3541	$51.35	$51.35	$51.40
Purchase #5	$91.79	9.316%	$100.3412	$100.34	$100.35	$100.30
Purchase #6	$126.46	11.421%	$140.903	$140.90	$140.90	$140.90
Purchase #7	$103.42	5.727%	$109.3429	$109.34	$109.35	$109.30
7 purchase totals =	$899.10		$968.8230	$968.81	$968.80	$968.80