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	$216.78	4.642%	$226.8429	$226.84	$226.85	$226.80
Purchase #2	$178.53	7.207%	$191.3967	$191.40	$191.40	$191.40
Purchase #3	$247.89	3.866%	$257.4734	$257.47	$257.45	$257.50
Purchase #4	$58.58	11.135%	$65.1029	$65.10	$65.10	$65.10
Purchase #5	$43.90	3.410%	$45.397	$45.40	$45.40	$45.40
Purchase #6	$178.86	12.118%	$200.5343	$200.53	$200.55	$200.50
Purchase #7	$48.91	12.381%	$54.9655	$54.97	$54.95	$55.00
7 purchase totals =	$973.45		$1,041.7127	$1,041.71	$1,041.70	$1,041.70