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	$121.84	5.238%	$128.222	$128.22	$128.20	$128.20
Purchase #2	$207.90	4.650%	$217.5674	$217.57	$217.55	$217.60
Purchase #3	$125.29	12.228%	$140.6105	$140.61	$140.60	$140.60
Purchase #4	$57.50	13.301%	$65.1481	$65.15	$65.15	$65.10
Purchase #5	$222.54	8.358%	$241.1399	$241.14	$241.15	$241.10
Purchase #6	$67.90	3.592%	$70.339	$70.34	$70.35	$70.30
Purchase #7	$226.33	9.759%	$248.4175	$248.42	$248.40	$248.40
7 purchase totals =	$1,029.30		$1,111.4444	$1,111.45	$1,111.40	$1,111.30