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	$156.55	10.791%	$173.4433	$173.44	$173.45	$173.40
Purchase #2	$193.83	3.302%	$200.2303	$200.23	$200.25	$200.20
Purchase #3	$103.85	5.539%	$109.6023	$109.60	$109.60	$109.60
Purchase #4	$189.65	10.383%	$209.3414	$209.34	$209.35	$209.30
Purchase #5	$175.81	11.744%	$196.4571	$196.46	$196.45	$196.50
Purchase #6	$121.29	7.244%	$130.0762	$130.08	$130.10	$130.10
Purchase #7	$117.98	4.853%	$123.7056	$123.71	$123.70	$123.70
7 purchase totals =	$1,058.96		$1,142.8562	$1,142.86	$1,142.90	$1,142.80