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	$78.81	8.242%	$85.3055	$85.31	$85.30	$85.30
Purchase #2	$198.25	10.696%	$219.4548	$219.45	$219.45	$219.50
Purchase #3	$78.38	4.442%	$81.8616	$81.86	$81.85	$81.90
Purchase #4	$211.73	4.155%	$220.5274	$220.53	$220.55	$220.50
Purchase #5	$212.91	13.447%	$241.54	$241.54	$241.55	$241.50
Purchase #6	$88.42	9.563%	$96.8756	$96.88	$96.90	$96.90
Purchase #7	$113.42	4.231%	$118.2188	$118.22	$118.20	$118.20
7 purchase totals =	$981.92		$1,063.7837	$1,063.79	$1,063.80	$1,063.80