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	$77.74	10.717%	$86.0714	$86.07	$86.05	$86.10
Purchase #2	$72.37	11.656%	$80.8054	$80.81	$80.80	$80.80
Purchase #3	$203.60	3.773%	$211.2818	$211.28	$211.30	$211.30
Purchase #4	$85.82	4.550%	$89.7248	$89.72	$89.70	$89.70
Purchase #5	$14.81	3.553%	$15.3362	$15.34	$15.35	$15.30
Purchase #6	$156.49	5.190%	$164.6118	$164.61	$164.60	$164.60
Purchase #7	$7.66	12.298%	$8.602	$8.60	$8.60	$8.60
7 purchase totals =	$618.49		$656.4334	$656.43	$656.40	$656.40