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	$237.40	7.847%	$256.0288	$256.03	$256.05	$256.00
Purchase #2	$185.98	13.470%	$211.0315	$211.03	$211.05	$211.00
Purchase #3	$25.42	9.645%	$27.8718	$27.87	$27.85	$27.90
Purchase #4	$150.58	12.634%	$169.6043	$169.60	$169.60	$169.60
Purchase #5	$97.60	6.172%	$103.6239	$103.62	$103.60	$103.60
Purchase #6	$225.54	8.773%	$245.3266	$245.33	$245.35	$245.30
Purchase #7	$92.36	9.160%	$100.8202	$100.82	$100.80	$100.80
7 purchase totals =	$1,014.88		$1,114.3071	$1,114.30	$1,114.30	$1,114.20