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	$232.64	9.767%	$255.3619	$255.36	$255.35	$255.40
Purchase #2	$64.50	11.770%	$72.0917	$72.09	$72.10	$72.10
Purchase #3	$232.46	12.175%	$260.762	$260.76	$260.75	$260.80
Purchase #4	$55.58	9.818%	$61.0368	$61.04	$61.05	$61.00
Purchase #5	$49.36	4.581%	$51.6212	$51.62	$51.60	$51.60
Purchase #6	$181.63	9.742%	$199.3244	$199.32	$199.30	$199.30
Purchase #7	$196.48	7.537%	$211.2887	$211.29	$211.30	$211.30
7 purchase totals =	$1,012.65		$1,111.4867	$1,111.48	$1,111.45	$1,111.50