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	$106.39	3.140%	$109.7306	$109.73	$109.75	$109.70
Purchase #2	$81.41	5.395%	$85.8021	$85.80	$85.80	$85.80
Purchase #3	$188.65	13.338%	$213.8121	$213.81	$213.80	$213.80
Purchase #4	$100.39	10.841%	$111.2733	$111.27	$111.25	$111.30
Purchase #5	$21.99	7.604%	$23.6621	$23.66	$23.65	$23.70
Purchase #6	$94.61	5.587%	$99.8959	$99.90	$99.90	$99.90
Purchase #7	$194.33	5.492%	$205.0026	$205.00	$205.00	$205.00
7 purchase totals =	$787.77		$849.1787	$849.17	$849.15	$849.20