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	$154.69	8.778%	$168.2687	$168.27	$168.25	$168.30
Purchase #2	$13.69	3.635%	$14.1876	$14.19	$14.20	$14.20
Purchase #3	$137.76	3.430%	$142.4852	$142.49	$142.50	$142.50
Purchase #4	$152.41	6.850%	$162.8501	$162.85	$162.85	$162.90
Purchase #5	$221.30	13.353%	$250.8502	$250.85	$250.85	$250.90
Purchase #6	$212.69	13.681%	$241.7881	$241.79	$241.80	$241.80
Purchase #7	$36.83	5.434%	$38.8313	$38.83	$38.85	$38.80
7 purchase totals =	$929.37		$1,019.2612	$1,019.27	$1,019.30	$1,019.40