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	$240.61	5.314%	$253.396	$253.40	$253.40	$253.40
Purchase #2	$21.52	10.372%	$23.7521	$23.75	$23.75	$23.80
Purchase #3	$47.75	10.696%	$52.8573	$52.86	$52.85	$52.90
Purchase #4	$29.52	13.617%	$33.5397	$33.54	$33.55	$33.50
Purchase #5	$156.63	5.775%	$165.6754	$165.68	$165.70	$165.70
Purchase #6	$137.53	13.356%	$155.8985	$155.90	$155.90	$155.90
Purchase #7	$37.28	9.229%	$40.7206	$40.72	$40.70	$40.70
7 purchase totals =	$670.84		$725.8396	$725.85	$725.85	$725.90