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	$90.32	9.185%	$98.6159	$98.62	$98.60	$98.60
Purchase #2	$50.28	5.481%	$53.0358	$53.04	$53.05	$53.00
Purchase #3	$162.71	3.214%	$167.9395	$167.94	$167.95	$167.90
Purchase #4	$139.40	12.634%	$157.0118	$157.01	$157.00	$157.00
Purchase #5	$215.82	8.298%	$233.7287	$233.73	$233.75	$233.70
Purchase #6	$72.71	13.230%	$82.3295	$82.33	$82.35	$82.30
Purchase #7	$223.64	8.434%	$242.5018	$242.50	$242.50	$242.50
7 purchase totals =	$954.88		$1,035.1630	$1,035.17	$1,035.20	$1,035.00