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	$82.88	8.483%	$89.9107	$89.91	$89.90	$89.90
Purchase #2	$123.75	10.207%	$136.3812	$136.38	$136.40	$136.40
Purchase #3	$149.27	10.488%	$164.9254	$164.93	$164.95	$164.90
Purchase #4	$217.83	9.457%	$238.4302	$238.43	$238.45	$238.40
Purchase #5	$166.63	5.543%	$175.8663	$175.87	$175.85	$175.90
Purchase #6	$83.35	12.772%	$93.9955	$94.00	$94.00	$94.00
Purchase #7	$200.40	7.733%	$215.8969	$215.90	$215.90	$215.90
7 purchase totals =	$1,024.11		$1,115.4062	$1,115.42	$1,115.45	$1,115.40