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	$62.58	3.219%	$64.5945	$64.59	$64.60	$64.60
Purchase #2	$93.89	6.617%	$100.1027	$100.10	$100.10	$100.10
Purchase #3	$61.89	7.651%	$66.6252	$66.63	$66.65	$66.60
Purchase #4	$109.51	6.692%	$116.8384	$116.84	$116.85	$116.80
Purchase #5	$139.71	6.296%	$148.5061	$148.51	$148.50	$148.50
Purchase #6	$198.31	3.416%	$205.0843	$205.08	$205.10	$205.10
Purchase #7	$243.33	11.396%	$271.0599	$271.06	$271.05	$271.10
7 purchase totals =	$909.22		$972.8111	$972.81	$972.85	$972.80