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	$235.94	10.440%	$260.5721	$260.57	$260.55	$260.60
Purchase #2	$250.98	6.818%	$268.0918	$268.09	$268.10	$268.10
Purchase #3	$69.95	3.343%	$72.2884	$72.29	$72.30	$72.30
Purchase #4	$171.68	5.534%	$181.1808	$181.18	$181.20	$181.20
Purchase #5	$237.48	9.390%	$259.7794	$259.78	$259.80	$259.80
Purchase #6	$70.87	10.825%	$78.5417	$78.54	$78.55	$78.50
Purchase #7	$49.65	3.818%	$51.5456	$51.55	$51.55	$51.50
7 purchase totals =	$1,086.55		$1,171.9998	$1,172.00	$1,172.05	$1,172.00