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	$181.89	3.641%	$188.5126	$188.51	$188.50	$188.50
Purchase #2	$114.70	5.128%	$120.5818	$120.58	$120.60	$120.60
Purchase #3	$101.37	13.527%	$115.0823	$115.08	$115.10	$115.10
Purchase #4	$239.98	12.649%	$270.3351	$270.34	$270.35	$270.30
Purchase #5	$203.54	5.592%	$214.922	$214.92	$214.90	$214.90
Purchase #6	$82.29	3.359%	$85.0541	$85.05	$85.05	$85.10
Purchase #7	$171.96	10.816%	$190.5592	$190.56	$190.55	$190.60
7 purchase totals =	$1,095.73		$1,185.0471	$1,185.04	$1,185.05	$1,185.10