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	$119.93	7.805%	$129.2905	$129.29	$129.30	$129.30
Purchase #2	$169.60	5.296%	$178.582	$178.58	$178.60	$178.60
Purchase #3	$122.39	3.805%	$127.0469	$127.05	$127.05	$127.00
Purchase #4	$218.74	11.658%	$244.2407	$244.24	$244.25	$244.20
Purchase #5	$87.80	4.818%	$92.0302	$92.03	$92.05	$92.00
Purchase #6	$85.84	5.116%	$90.2316	$90.23	$90.25	$90.20
Purchase #7	$137.44	13.470%	$155.9532	$155.95	$155.95	$156.00
7 purchase totals =	$941.74		$1,017.3751	$1,017.37	$1,017.45	$1,017.30