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	$239.64	7.834%	$258.4134	$258.41	$258.40	$258.40
Purchase #2	$241.40	3.589%	$250.0638	$250.06	$250.05	$250.10
Purchase #3	$55.65	3.580%	$57.6423	$57.64	$57.65	$57.60
Purchase #4	$28.80	9.264%	$31.468	$31.47	$31.45	$31.50
Purchase #5	$148.68	10.722%	$164.6215	$164.62	$164.60	$164.60
Purchase #6	$191.57	8.588%	$208.022	$208.02	$208.00	$208.00
Purchase #7	$96.50	6.228%	$102.51	$102.51	$102.50	$102.50
7 purchase totals =	$1,002.24		$1,072.7410	$1,072.73	$1,072.65	$1,072.70