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	$149.54	9.788%	$164.177	$164.18	$164.20	$164.20
Purchase #2	$242.86	9.158%	$265.1011	$265.10	$265.10	$265.10
Purchase #3	$162.94	12.226%	$182.861	$182.86	$182.85	$182.90
Purchase #4	$145.76	7.258%	$156.3393	$156.34	$156.35	$156.30
Purchase #5	$41.69	5.502%	$43.9838	$43.98	$44.00	$44.00
Purchase #6	$248.74	8.365%	$269.5471	$269.55	$269.55	$269.50
Purchase #7	$69.34	12.590%	$78.0699	$78.07	$78.05	$78.10
7 purchase totals =	$1,060.87		$1,160.0792	$1,160.08	$1,160.10	$1,160.10