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	$204.39	4.490%	$213.5671	$213.57	$213.55	$213.60
Purchase #2	$173.99	6.513%	$185.322	$185.32	$185.30	$185.30
Purchase #3	$76.31	8.641%	$82.9039	$82.90	$82.90	$82.90
Purchase #4	$106.32	8.568%	$115.4295	$115.43	$115.45	$115.40
Purchase #5	$130.98	4.127%	$136.3855	$136.39	$136.40	$136.40
Purchase #6	$201.88	12.256%	$226.6224	$226.62	$226.60	$226.60
Purchase #7	$51.98	13.666%	$59.0836	$59.08	$59.10	$59.10
7 purchase totals =	$945.85		$1,019.3140	$1,019.31	$1,019.30	$1,019.30