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	$168.43	9.596%	$184.5925	$184.59	$184.60	$184.60
Purchase #2	$135.86	11.317%	$151.2353	$151.24	$151.25	$151.20
Purchase #3	$139.58	6.678%	$148.9012	$148.90	$148.90	$148.90
Purchase #4	$164.37	5.730%	$173.7884	$173.79	$173.80	$173.80
Purchase #5	$234.28	10.609%	$259.1348	$259.13	$259.15	$259.10
Purchase #6	$63.85	11.696%	$71.3179	$71.32	$71.30	$71.30
Purchase #7	$25.65	9.129%	$27.9916	$27.99	$28.00	$28.00
7 purchase totals =	$932.02		$1,016.9617	$1,016.96	$1,017.00	$1,016.90