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	$114.33	10.253%	$126.0523	$126.05	$126.05	$126.10
Purchase #2	$227.65	7.700%	$245.1791	$245.18	$245.20	$245.20
Purchase #3	$174.83	12.152%	$196.0753	$196.08	$196.10	$196.10
Purchase #4	$52.49	5.559%	$55.4079	$55.41	$55.40	$55.40
Purchase #5	$245.94	5.526%	$259.5306	$259.53	$259.55	$259.50
Purchase #6	$171.26	6.622%	$182.6008	$182.60	$182.60	$182.60
Purchase #7	$103.63	12.852%	$116.9485	$116.95	$116.95	$116.90
7 purchase totals =	$1,090.13		$1,181.7945	$1,181.80	$1,181.85	$1,181.80