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	$230.27	5.554%	$243.0592	$243.06	$243.05	$243.10
Purchase #2	$72.67	12.638%	$81.854	$81.85	$81.85	$81.90
Purchase #3	$57.28	11.647%	$63.9514	$63.95	$63.95	$64.00
Purchase #4	$37.26	11.522%	$41.5531	$41.55	$41.55	$41.60
Purchase #5	$7.28	3.323%	$7.5219	$7.52	$7.50	$7.50
Purchase #6	$208.93	4.412%	$218.148	$218.15	$218.15	$218.10
Purchase #7	$39.83	9.163%	$43.4796	$43.48	$43.50	$43.50
7 purchase totals =	$653.52		$699.5672	$699.56	$699.55	$699.70