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	$98.96	12.250%	$111.0826	$111.08	$111.10	$111.10
Purchase #2	$166.28	13.285%	$188.3703	$188.37	$188.35	$188.40
Purchase #3	$96.54	7.491%	$103.7718	$103.77	$103.75	$103.80
Purchase #4	$181.94	13.575%	$206.6384	$206.64	$206.65	$206.60
Purchase #5	$45.52	13.449%	$51.642	$51.64	$51.65	$51.60
Purchase #6	$125.35	8.704%	$136.2605	$136.26	$136.25	$136.30
Purchase #7	$211.86	3.734%	$219.7709	$219.77	$219.75	$219.80
7 purchase totals =	$926.45		$1,017.5365	$1,017.53	$1,017.50	$1,017.60