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	$11.41	4.627%	$11.9379	$11.94	$11.95	$11.90
Purchase #2	$39.43	10.816%	$43.6947	$43.69	$43.70	$43.70
Purchase #3	$178.59	5.447%	$188.3178	$188.32	$188.30	$188.30
Purchase #4	$48.79	12.156%	$54.7209	$54.72	$54.70	$54.70
Purchase #5	$28.66	11.806%	$32.0436	$32.04	$32.05	$32.00
Purchase #6	$89.35	13.203%	$101.1469	$101.15	$101.15	$101.10
Purchase #7	$237.41	5.331%	$250.0663	$250.07	$250.05	$250.10
7 purchase totals =	$633.64		$681.9281	$681.93	$681.90	$681.80