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	$35.60	8.690%	$38.6936	$38.69	$38.70	$38.70
Purchase #2	$82.58	9.192%	$90.1708	$90.17	$90.15	$90.20
Purchase #3	$92.88	8.802%	$101.0553	$101.06	$101.05	$101.10
Purchase #4	$50.57	13.273%	$57.2822	$57.28	$57.30	$57.30
Purchase #5	$113.33	9.252%	$123.8153	$123.82	$123.80	$123.80
Purchase #6	$196.74	8.691%	$213.8387	$213.84	$213.85	$213.80
Purchase #7	$126.54	8.600%	$137.4224	$137.42	$137.40	$137.40
7 purchase totals =	$698.24		$762.2783	$762.28	$762.25	$762.30