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	$55.32	3.299%	$57.145	$57.15	$57.15	$57.10
Purchase #2	$54.92	4.566%	$57.4276	$57.43	$57.45	$57.40
Purchase #3	$196.53	9.686%	$215.5659	$215.57	$215.55	$215.60
Purchase #4	$112.94	7.148%	$121.013	$121.01	$121.00	$121.00
Purchase #5	$157.34	6.790%	$168.0234	$168.02	$168.00	$168.00
Purchase #6	$55.31	11.320%	$61.5711	$61.57	$61.55	$61.60
Purchase #7	$176.81	13.492%	$200.6652	$200.67	$200.65	$200.70
7 purchase totals =	$809.17		$881.4112	$881.42	$881.35	$881.40