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	$121.40	5.549%	$128.1365	$128.14	$128.15	$128.10
Purchase #2	$215.31	3.349%	$222.5207	$222.52	$222.50	$222.50
Purchase #3	$228.92	9.406%	$250.4522	$250.45	$250.45	$250.50
Purchase #4	$191.38	9.415%	$209.3984	$209.40	$209.40	$209.40
Purchase #5	$56.30	12.415%	$63.2896	$63.29	$63.30	$63.30
Purchase #6	$159.63	11.474%	$177.9459	$177.95	$177.95	$177.90
Purchase #7	$86.47	6.561%	$92.1433	$92.14	$92.15	$92.10
7 purchase totals =	$1,059.41		$1,143.8866	$1,143.89	$1,143.90	$1,143.80