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	$208.96	9.407%	$228.6169	$228.62	$228.60	$228.60
Purchase #2	$225.76	13.777%	$256.863	$256.86	$256.85	$256.90
Purchase #3	$57.29	8.651%	$62.2462	$62.25	$62.25	$62.20
Purchase #4	$82.66	10.436%	$91.2864	$91.29	$91.30	$91.30
Purchase #5	$162.46	3.357%	$167.9138	$167.91	$167.90	$167.90
Purchase #6	$62.92	13.392%	$71.3462	$71.35	$71.35	$71.30
Purchase #7	$125.65	4.405%	$131.1849	$131.18	$131.20	$131.20
7 purchase totals =	$925.70		$1,009.4574	$1,009.46	$1,009.45	$1,009.40