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	$205.94	5.235%	$216.721	$216.72	$216.70	$216.70
Purchase #2	$245.56	5.666%	$259.4734	$259.47	$259.45	$259.50
Purchase #3	$62.43	4.242%	$65.0783	$65.08	$65.10	$65.10
Purchase #4	$130.90	4.627%	$136.9567	$136.96	$136.95	$137.00
Purchase #5	$49.69	7.708%	$53.5201	$53.52	$53.50	$53.50
Purchase #6	$137.51	11.588%	$153.4447	$153.44	$153.45	$153.40
Purchase #7	$199.61	5.772%	$211.1315	$211.13	$211.15	$211.10
7 purchase totals =	$1,031.64		$1,096.3257	$1,096.32	$1,096.30	$1,096.30