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	$179.88	13.136%	$203.509	$203.51	$203.50	$203.50
Purchase #2	$96.63	3.102%	$99.6275	$99.63	$99.65	$99.60
Purchase #3	$164.60	12.787%	$185.6474	$185.65	$185.65	$185.60
Purchase #4	$77.70	4.111%	$80.8942	$80.89	$80.90	$80.90
Purchase #5	$175.60	9.492%	$192.268	$192.27	$192.25	$192.30
Purchase #6	$240.27	11.181%	$267.1346	$267.13	$267.15	$267.10
Purchase #7	$185.85	8.109%	$200.9206	$200.92	$200.90	$200.90
7 purchase totals =	$1,120.53		$1,230.0013	$1,230.00	$1,230.00	$1,229.90