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	$228.32	12.839%	$257.634	$257.63	$257.65	$257.60
Purchase #2	$203.28	12.347%	$228.379	$228.38	$228.40	$228.40
Purchase #3	$180.81	8.789%	$196.7014	$196.70	$196.70	$196.70
Purchase #4	$204.78	9.451%	$224.1338	$224.13	$224.15	$224.10
Purchase #5	$67.65	7.168%	$72.4992	$72.50	$72.50	$72.50
Purchase #6	$83.72	3.674%	$86.7959	$86.80	$86.80	$86.80
Purchase #7	$142.25	9.721%	$156.0781	$156.08	$156.10	$156.10
7 purchase totals =	$1,110.81		$1,222.2214	$1,222.22	$1,222.30	$1,222.20