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	$64.64	8.180%	$69.9276	$69.93	$69.95	$69.90
Purchase #2	$191.82	9.139%	$209.3504	$209.35	$209.35	$209.40
Purchase #3	$191.71	4.492%	$200.3216	$200.32	$200.30	$200.30
Purchase #4	$144.93	9.500%	$158.6984	$158.70	$158.70	$158.70
Purchase #5	$250.25	5.817%	$264.807	$264.81	$264.80	$264.80
Purchase #6	$136.37	4.443%	$142.4289	$142.43	$142.45	$142.40
Purchase #7	$238.88	10.526%	$264.0245	$264.02	$264.00	$264.00
7 purchase totals =	$1,218.60		$1,309.5584	$1,309.56	$1,309.55	$1,309.50