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	$167.44	13.714%	$190.4027	$190.40	$190.40	$190.40
Purchase #2	$30.63	12.236%	$34.3779	$34.38	$34.40	$34.40
Purchase #3	$86.54	3.243%	$89.3465	$89.35	$89.35	$89.30
Purchase #4	$5.25	13.743%	$5.9715	$5.97	$5.95	$6.00
Purchase #5	$224.39	12.768%	$253.0401	$253.04	$253.05	$253.00
Purchase #6	$73.55	6.663%	$78.4506	$78.45	$78.45	$78.50
Purchase #7	$93.64	10.729%	$103.6866	$103.69	$103.70	$103.70
7 purchase totals =	$681.44		$755.2759	$755.28	$755.30	$755.30