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	$107.99	4.436%	$112.7804	$112.78	$112.80	$112.80
Purchase #2	$89.83	9.545%	$98.4043	$98.40	$98.40	$98.40
Purchase #3	$102.76	12.647%	$115.7561	$115.76	$115.75	$115.80
Purchase #4	$240.94	7.326%	$258.5913	$258.59	$258.60	$258.60
Purchase #5	$110.43	11.738%	$123.3923	$123.39	$123.40	$123.40
Purchase #6	$92.40	8.809%	$100.5395	$100.54	$100.55	$100.50
Purchase #7	$159.28	10.421%	$175.8786	$175.88	$175.90	$175.90
7 purchase totals =	$903.63		$985.3425	$985.34	$985.40	$985.40