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	$157.50	9.192%	$171.9774	$171.98	$172.00	$172.00
Purchase #2	$92.81	8.282%	$100.4965	$100.50	$100.50	$100.50
Purchase #3	$190.99	6.841%	$204.0556	$204.06	$204.05	$204.10
Purchase #4	$62.88	10.737%	$69.6314	$69.63	$69.65	$69.60
Purchase #5	$136.64	4.362%	$142.6002	$142.60	$142.60	$142.60
Purchase #6	$171.34	9.411%	$187.4648	$187.46	$187.45	$187.50
Purchase #7	$217.53	5.433%	$229.3484	$229.35	$229.35	$229.30
7 purchase totals =	$1,029.69		$1,105.5743	$1,105.58	$1,105.60	$1,105.60