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	$208.93	9.250%	$228.256	$228.26	$228.25	$228.30
Purchase #2	$174.40	10.622%	$192.9248	$192.92	$192.90	$192.90
Purchase #3	$55.82	11.301%	$62.1282	$62.13	$62.15	$62.10
Purchase #4	$163.42	13.596%	$185.6386	$185.64	$185.65	$185.60
Purchase #5	$191.66	4.572%	$200.4227	$200.42	$200.40	$200.40
Purchase #6	$61.92	8.404%	$67.1238	$67.12	$67.10	$67.10
Purchase #7	$73.51	7.186%	$78.7924	$78.79	$78.80	$78.80
7 purchase totals =	$929.66		$1,015.2865	$1,015.28	$1,015.25	$1,015.20