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	$134.94	12.759%	$152.157	$152.16	$152.15	$152.20
Purchase #2	$156.74	5.192%	$164.8779	$164.88	$164.90	$164.90
Purchase #3	$55.32	11.315%	$61.5795	$61.58	$61.60	$61.60
Purchase #4	$219.97	12.873%	$248.2867	$248.29	$248.30	$248.30
Purchase #5	$67.97	7.443%	$73.029	$73.03	$73.05	$73.00
Purchase #6	$187.99	4.470%	$196.3932	$196.39	$196.40	$196.40
Purchase #7	$111.37	3.710%	$115.5018	$115.50	$115.50	$115.50
7 purchase totals =	$934.30		$1,011.8251	$1,011.83	$1,011.90	$1,011.90