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	$34.32	4.817%	$35.9732	$35.97	$35.95	$36.00
Purchase #2	$52.56	4.359%	$54.8511	$54.85	$54.85	$54.90
Purchase #3	$160.83	8.388%	$174.3204	$174.32	$174.30	$174.30
Purchase #4	$167.49	6.294%	$178.0318	$178.03	$178.05	$178.00
Purchase #5	$90.94	4.873%	$95.3715	$95.37	$95.35	$95.40
Purchase #6	$89.54	4.208%	$93.3078	$93.31	$93.30	$93.30
Purchase #7	$86.81	13.619%	$98.6327	$98.63	$98.65	$98.60
7 purchase totals =	$682.49		$730.4885	$730.48	$730.45	$730.50