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	$215.56	6.450%	$229.4636	$229.46	$229.45	$229.50
Purchase #2	$50.85	11.247%	$56.5691	$56.57	$56.55	$56.60
Purchase #3	$182.32	7.792%	$196.5264	$196.53	$196.55	$196.50
Purchase #4	$62.85	13.767%	$71.5026	$71.50	$71.50	$71.50
Purchase #5	$185.44	13.699%	$210.8434	$210.84	$210.85	$210.80
Purchase #6	$113.55	8.589%	$123.3028	$123.30	$123.30	$123.30
Purchase #7	$202.93	6.329%	$215.7734	$215.77	$215.75	$215.80
7 purchase totals =	$1,013.50		$1,103.9813	$1,103.97	$1,103.95	$1,104.00