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	$201.38	12.393%	$226.337	$226.34	$226.35	$226.30
Purchase #2	$204.66	9.284%	$223.6606	$223.66	$223.65	$223.70
Purchase #3	$250.25	5.221%	$263.3156	$263.32	$263.30	$263.30
Purchase #4	$54.82	13.686%	$62.3227	$62.32	$62.30	$62.30
Purchase #5	$104.83	4.825%	$109.888	$109.89	$109.90	$109.90
Purchase #6	$221.31	9.701%	$242.7793	$242.78	$242.80	$242.80
Purchase #7	$163.56	10.834%	$181.2801	$181.28	$181.30	$181.30
7 purchase totals =	$1,200.81		$1,309.5833	$1,309.59	$1,309.60	$1,309.60