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	$203.60	3.838%	$211.4142	$211.41	$211.40	$211.40
Purchase #2	$39.28	13.326%	$44.5145	$44.51	$44.50	$44.50
Purchase #3	$162.80	12.433%	$183.0409	$183.04	$183.05	$183.00
Purchase #4	$34.59	10.357%	$38.1725	$38.17	$38.15	$38.20
Purchase #5	$142.28	3.292%	$146.9639	$146.96	$146.95	$147.00
Purchase #6	$181.82	8.206%	$196.7401	$196.74	$196.75	$196.70
Purchase #7	$37.72	6.266%	$40.0835	$40.08	$40.10	$40.10
7 purchase totals =	$802.09		$860.9296	$860.91	$860.90	$860.90