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	$156.98	9.200%	$171.4222	$171.42	$171.40	$171.40
Purchase #2	$200.79	8.805%	$218.4696	$218.47	$218.45	$218.50
Purchase #3	$80.48	5.869%	$85.2034	$85.20	$85.20	$85.20
Purchase #4	$229.69	5.298%	$241.859	$241.86	$241.85	$241.90
Purchase #5	$137.41	5.841%	$145.4361	$145.44	$145.45	$145.40
Purchase #6	$163.27	13.537%	$185.3719	$185.37	$185.35	$185.40
Purchase #7	$117.57	12.179%	$131.8889	$131.89	$131.90	$131.90
7 purchase totals =	$1,086.19		$1,179.6511	$1,179.65	$1,179.60	$1,179.70